System and method for linearizing a CMOS differential pair

• US 6,985,035 B1
• Filed: 05/17/2000
• Issued: 01/10/2006
• Est. Priority Date: 11/12/1998
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Khorramabadi, Haideh
• Primary Examiner(s): NGUYEN, PATRICIA T
• Application Number:
  US09/573,356
• Time in Patent Office: 2,064 Days
• Field of Search: 330/253, 330/149, 330/252, 330/307
• US Class Current: 330/253
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 2017/0026 Multilayer LC-filter
• CPC Class Codes: H01F 2017/0046 with a conductive path having a bridge
• CPC Class Codes: H01F 2017/0073 with a special conductive pattern, e.g. flat spiral
• CPC Class Codes: H01L 23/5227 Inductive arrangements or effects of, or between, wiring layers other inductive arrangements H01L23/645
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/364 the amplifier comprising field effect transistors H03B5/366 takes precedence
• CPC Class Codes: H03F 1/26 Modifications of amplifiers to reduce influence of noise generated by amplifying elements
• CPC Class Codes: H03F 1/3211 in differential amplifiers
• CPC Class Codes: H03F 2200/294 the amplifier being a low noise amplifier [LNA]
• CPC Class Codes: H03F 2200/372 Noise reduction and elimination in amplifier
• CPC Class Codes: H03F 2203/45366 the AAC comprising multiple transistors parallel coupled at their gates only, e.g. in a cascode dif amp, only those forming the composite common source transistor
• CPC Class Codes: H03F 2203/45631 the LC comprising one or more capacitors, e.g. coupling capacitors
• CPC Class Codes: H03F 2203/45644 the LC comprising a cross coupling circuit, e.g. comprising two cross-coupled transistors
• CPC Class Codes: H03F 2203/45652 the LC comprising one or more further dif amp stages, either identical to the dif amp or not, in cascade
• CPC Class Codes: H03F 3/195 in integrated circuits
• CPC Class Codes: H03F 3/45192 : Folded cascode stages
• CPC Class Codes: H03F 3/68 : Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics power amplifiers using a combination of several semiconductor amplifiers H03F3/211; combinations of amplifiers using coupling networks with distributed constants H03F3/602
• CPC Class Codes: H03H 11/04 : Frequency selective two-port networks
• CPC Class Codes: H03H 11/10 : using negative impedance converters H03H11/08 takes precedence
• CPC Class Codes: H03H 11/1291 : Current or voltage controlled filters
• CPC Class Codes: H03H 11/245 : using field-effect transistor
• CPC Class Codes: H03H 7/25 : comprising an element controlled by an electric or magnetic variable H03H7/27 takes precedence

Abstract

An integrated receiver with channel selection and image rejection substantially implemented on a single CMOS integrated circuit. A receiver front end provides programmable attenuation and a programmable gain low noise amplifier. LC filters integrated onto the substrate in conjunction with image reject mixers provide image frequency rejection. Filter tuning and inductor Q compensation over temperature are performed on chip. Active filters utilize multi track spiral inductors with shields to increase circuit Q. The filters incorporate a gain stage that provides improved dynamic range through the use of cross coupled auxiliary differential pair CMOS amplifiers to cancel distortion in a main linearized differential pair amplifier. Frequency planning provides additional image rejection. Local oscillator signal generation methods on chip reduce distortion. A PLL generates needed out of band LO signals. Direct synthesis generates in band LO signals. PLL VCOs are centered automatically. A differential crystal oscillator provides a frequency reference. Differential signal transmission throughout the receiver is used. ESD protection is provided by a pad ring and ESD clamping structure. Shunts utilize a gate boosting at each pin to discharge ESD build up. An IF VGA utilizes distortion cancellation achieved with cross coupled differential pair amplifiers having their V_ds dynamically modified in conjunction with current steering of the differential pairs sources.

Claims

1. A method for generating an effective overall transconductance in an amplifier comprising:

generating a first transconductance from a main differential pair amplifier that is centered about a zero offset voltage;

generating a second transconductance from a first differential error amplifier that is symmetrically centered about a negative non zero offset voltage;

generating a third transconductance from a second differential error amplifier that is symmetrically centered about a positive non zero offset voltage;

adding the second transconductance to the third transconductance to form an error transconductance; and

subtracting the error transconductance from the first transconductance to form the effective overall transconductance.

2. A method for reducing differential pair amplifier distortion comprising:

fabricating a differential pair amplifier on a substrate having a pair of MOS transistors each having a channel defined by a first length and a first width;

fabricating a first differential pair error amplifier on the substrate having a pair of MOS transistors each having a channel defined by the first length and a second width;

fabricating a second differential pair error amplifier on the substrate having a pair of MOS transistors each having a channel defined by the first length and a third width; and

coupling the first differential pair error amplifier to the second differential pair error amplifier and the differential pair amplifier.

3. A differential amplifier comprising:

a main differential pair of FET transistors formed by a first transistor of the main differential pair and a second transistor of the main differential pair having a first input of the main differential pair formed by a gate of the first transistor of the main differential pair, having a second input of the main differential pair formed by a gate of the second transistor of the main differential pair, having a first current output of the main differential pair formed by a first drain of the first transistor of the main differential pair, having a second current output of the main differential pair formed by a drain of the second transistor of the main differential pair, with a main differential pair common source connection formed by a source of the first transistor of the main differential pair coupled to a source of the second transistor of the main differential pair;

a main differential pair current source for producing a substantially constant direct current coupled to the main differential pair common source connection;

a first auxiliary differential pair of FET transistors formed by a first transistor of the first auxiliary differential pair and a second transistor of the first auxiliary differential pair having a first input of the first auxiliary differential pair formed by a gate of the first transistor of the first auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the first auxiliary differential pair formed by a gate of the second transistor of the first auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the first auxiliary differential pair formed by a drain of the first transistor of the first auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the first auxiliary differential pair formed by a drain of the second transistor of the first auxiliary differential pair and coupled to the first current output of the main differential pair, with a first auxiliary differential pair common source connection formed by a source of the first transistor of the first auxiliary differential pair being coupled to a source of the second transistor of the first auxiliary differential pair;

a first auxiliary differential pair current source for producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the first auxiliary differential pair common source connection;

a second auxiliary differential pair of FET transistors formed by a first transistor of the second auxiliary differential pair and a second transistor of the second auxiliary differential pair having, a first input of the second auxiliary differential pair formed by a gate of the first transistor of the second auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the second auxiliary differential pair formed by a gate of the second transistor of the second auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the second auxiliary differential pair formed by a drain of the first transistor of the second auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the second auxiliary differential pair formed by a drain of the second transistor of the second auxiliary differential pair and coupled to the first current output of the main differential pair, with a second auxiliary differential pair common source connection formed by a source of the first transistor of the second auxiliary differential pair being coupled to a source of the second transistor of the second auxiliary differential pair; and

a second auxiliary differential pair current source for producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the second auxiliary differential pair common source connection;

wherein a first transconductance of the main differential pair of FET transistors is symmetrically centered about a zero offset voltage, and a second transconductance of the first auxiliary differential pair of FET transistors is symmetrically centered about a negative non-zero offset voltage, and a third transconductance of the second auxiliary differential pair of FET transistors is symmetrically centered about a positive non-zero offset voltage;

wherein said second transconductance is combined with said third transconductance to form an error transconductance;

wherein said error transconductance is subtracted from said first transconductance at the first and second drains of said main differential pair to reduce distortion in an output of the main differential pair.

4. The differential amplifier of claim 3, in which the first transistor of the first auxiliary differential pair has a first channel width to channel length ratio;

the second transistor of the second auxiliary differential pair has the first channel width to channel length ratio that is the same as the first channel width to channel length ratio of the first transistor of the first auxiliary differential pair;

the second transistor of the first auxiliary differential pair has a second channel width to length ratio; and

the first transistor of the second auxiliary differential pair has the second channel width to channel length ratio that is the same as the second channel width to channel length ratio of the second transistor of the first auxiliary differential pair, and the first channel width to channel length ratio is different from the second channel width to channel length ratio;

whereby a transistor offset voltage is created by the differing first channel width to channel length ratio to the second channel width to channel length ratio.

5. The differential amplifier of claim 4, in which the main differential pair generates a main differential pair transconductance set in magnitude by the current supplied by the main differential pair current source, the transconductance generated being a function of a differential input voltage impressed across the first input of the main differential pair and the second input of the main differential pair and having a maximum magnitude of transconductance at zero volts differential input voltage;

the first auxiliary differential pair generates a first auxiliary differential pair transconductance set in magnitude by the current supplied by the first auxiliary differential pair current source, the transconductance generated being a function of the differential input voltage impressed across the first input of the main differential pair and the second input of the main differential pair and having a maximum magnitude of transconductance at a differential input voltage equal to a value of the transistor offset voltage; and

the second auxiliary differential pair generates a second auxiliary differential pair transconductance set in magnitude by the current supplied by the second auxiliary differential pair current source, the transconductance generated being a function of the differential input voltage impressed across the first input of the main differential pair and the second input of the main differential pair and having a maximum magnitude of transconductance at a differential input voltage equal to a negative value of the transistor offset voltage;

whereby the main differential pair transconductance, first auxiliary differential pair transconductance, and second auxiliary differential pair transconductance superimpose to generate a resultant output current of the main differential pair that is substantially free from distortion over an increased range of differential input voltages.

6. A differential amplifier comprising:

a main differential pair of FET transistors formed by a first transistor of the main differential pair and a second transistor of the main differential pair having a first input of the main differential pair formed by a gate of the first transistor of the main differential pair, having a second input of the main differential pair formed by a gate of the second transistor of the main differential pair, having a first current output of the main differential pair formed by a first drain of the first transistor of the main differential pair, having a second current output of the main differential pair formed by a drain of the second transistor of the main differential pair, with a main differential pair common source connection formed by a source of the first transistor of the main differential pair coupled to a source of the second transistor of the main differential pair;

a main differential pair current source for producing a substantially constant direct current coupled to the main differential pair common source connection;

a first auxiliary differential pair of FET transistors formed by a first transistor of the first auxiliary differential pair and a second transistor of the first auxiliary differential pair having a first input of the first auxiliary differential pair formed by a gate of the first transistor of the first auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the first auxiliary differential pair formed by a gate of the second transistor of the first auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the first auxiliary differential pair formed by a drain of the first transistor of the first auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the first auxiliary differential pair formed by a drain of the second transistor of the first auxiliary differential pair and coupled to the first current output of the main differential pair, with a first auxiliary differential pair common source connection formed by a source of the first transistor of the first auxiliary differential pair being coupled to a source of the second transistor of the first auxiliary differential pair;

a first auxiliary differential pair current source for producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the first auxiliary differential pair common source connection;

a second auxiliary differential pair of FET transistors formed by a first transistor of the second auxiliary differential pair and a second transistor of the second auxiliary differential pair having, a first input of the second auxiliary differential pair formed by a gate of the first transistor of the second auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the second auxiliary differential pair formed by a gate of the second transistor of the second auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the second auxiliary differential pair formed by a drain of the first transistor of the second auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the second auxiliary differential pair formed by a drain of the second transistor of the second auxiliary differential pair and coupled to the first current output of the main differential pair, with a second auxiliary differential pair common source connection formed by a source of the first transistor of the second auxiliary differential pair being coupled to a source of the second transistor of the second auxiliary differential pair; and

a second auxiliary differential pair current source for producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the second auxiliary differential pair common source connection;

whereby drain currents of the first auxiliary differential pair and the second auxiliary differential pairs of transistors contribute to the drain currents of the main differential pair to reduce distortion in the main differential pair output;

wherein the first transistor of the first auxiliary differential pair has a first channel width to channel length ratio;

the second transistor of the second auxiliary differential pair has the first channel width to channel length ratio that is the same as the first channel width to channel length ratio of the first transistor of the first differential pair;

the second transistor of the first auxiliary differential pair has a second channel width to length ratio;

the first transistor of the second auxiliary differential pair has the second channel width to channel length ratio that is the same as the second channel width to channel length ratio of the second transistor of the first auxiliary differential pair, and the first channel width to channel length ratio is different from the second channel width to channel length ratio;

whereby a transistor offset voltage is created by the differing first channel width to channel length ratio to the second channel width to channel length ratio;

wherein the first transistor of the main differential pair has a channel length of 0.6 micro-meters and a channel width of 38 micro-meters;

the second transistor of the main differential pair has a channel length of 0.6 micro-meters and a channel width of 38 micro meters;

the main differential pair current source sources 9 miliamps of current;

the first transistor of the first auxiliary differential pair has a channel length of 0.6 micro-meters and a channel width of 3.9 micro meters;

the second transistor of the first auxiliary differential pair has a channel length of 0.6 micro-meters and a channel width of 10 micro meters;

the first auxiliary differential pair current source sources a current one sixteenth that of the main differential current source;

the first transistor of the second auxiliary differential pair has a channel length of 0.6 micro-meters and a channel width of 10 micro meters;

the second transistor of the second auxiliary differential pair has a channel length of 0.6 micro-meters and a channel width of 3.9 micro meters; and

the second auxiliary differential pair current source sources a current one sixteenth that of the main differential current source.

7. A differential amplifier comprising:

a main differential pair of FET transistors formed by a first transistor of the main differential pair and a second transistor of the main differential pair having a first input of the main differential pair formed by a gate of the first transistor of the main differential pair, having a second input of the main differential pair formed by a gate of the second transistor of the main differential pair, having a first current output of the main differential pair formed by a first drain of the first transistor of the main differential pair, having a second current output of the main differential pair formed by a drain of the second transistor of the main differential pair, with a main differential pair common source connection formed by a source of the first transistor of the main differential pair coupled to a source of the second transistor of the main differential pair;

a main differential pair current source for producing a substantially constant direct current coupled to the main differential pair common source connection;

a first auxiliary differential pair of FET transistors formed by a first transistor of the first auxiliary differential pair and a second transistor of the first auxiliary differential pair having a first input of the first auxiliary differential pair formed by a gate of the first transistor of the first auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the first auxiliary differential pair formed by a gate of the second transistor of the first auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the first auxiliary differential pair formed by a drain of the first transistor of the first auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the first auxiliary differential pair formed by a drain of the second transistor of the first auxiliary differential pair and coupled to the first current output of the main differential pair, with a first auxiliary differential pair common source connection formed by a source of the first transistor of the first auxiliary differential pair being coupled to a source of the second transistor of the first auxiliary differential pair;

a first auxiliary differential pair current source for producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the first auxiliary differential pair common source connection;

a second auxiliary differential pair of FET transistors formed by a first transistor of the second auxiliary differential pair and a second transistor of the second auxiliary differential pair having, a first input of the second auxiliary differential pair formed by a gate of the first transistor of the second auxiliary differential pair and coupled to the first input of the main differential pair, with a second input of the second auxiliary differential pair formed by a gate of the second transistor of the second auxiliary differential pair and coupled to the second input of the main differential pair, with a first current output of the second auxiliary differential pair formed by a drain of the first transistor of the second auxiliary differential pair and coupled to the second current output of the main differential pair, with a second current output of the second auxiliary differential pair formed by a drain of the second transistor of the second auxiliary differential pair and coupled to the first current output of the main differential pair, with a second auxiliary differential pair common source connection formed by a source of the first transistor of the second auxiliary differential pair being coupled to a source of the second transistor of the second auxiliary differential pair; and

a second auxiliary differential pair current source for o producing a substantially constant direct current that is a known fraction of the current produced by the main differential pair current source, coupled to the second auxiliary differential pair common source connection;

whereby drain currents of the first auxiliary differential pair and the second auxiliary differential pairs of transistors contribute to the drain currents of the main differential pair to reduce distortion in the main differential pair output

wherein the first transistor of the first auxiliary differential pair has a first channel width to channel length ratio;

the second transistor of the second auxiliary differential pair has the first channel width to channel length ratio that is the same as the first channel width to channel length ratio of the first transistor of the first differential pair;

the second transistor of the first auxiliary differential pair has a second channel width to length ratio;

the first transistor of the second auxiliary differential pair has the second channel width to channel length ratio that is the same as the second channel width to channel length ratio of the second transistor of the first auxiliary differential pair, and the first channel width to channel length ratio is different from the second channel width to channel length ratio;

whereby a transistor offset voltage is created by the differing first channel width to channel length ratio to the second channel width to channel length ratio;

wherein the first transistor of the main differential pair comprises a parallel combination of 20 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 1.9 micro meters;

the second transistor of the main differential pair comprises a parallel combination of 20 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 1.9 micro meters;

the first transistor of the first auxiliary differential pair comprises a parallel combination of 2 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 1.95 micro meters;

the second transistor of the first auxiliary differential pair comprises a parallel combination of 5 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 2 micro meters;

the first transistor of the second auxiliary differential pair comprises a parallel combination of 2 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 2 micro meters; and

the second transistor of the second auxiliary differential pair comprises a parallel combination of 2 discrete transistors each having a channel length of 0.6 micro-meters and a channel width of 1.95 micro meters.