Circuit arrangement for adjusting the impedance of a differential active component

• US 6,259,312 B1
• Filed: 03/09/1999
• Issued: 07/10/2001
• Est. Priority Date: 03/11/1998
• Status: Expired due to Term

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Mobile Phones UK Limited (Nokia Corporation)
• Inventors: Murtojarvi, Simo
• Primary Examiner(s): Wells, Kenneth B.
• Assistant Examiner(s): Nguyen, Hai L.
• Application Number:
  US09/265,165
• Publication Number:
  US 20010002113A1
• Time in Patent Office: 854 Days
• Field of Search: 327/560, 327/561, 327/562, 327/563, 327/306, 327/308, 327/309, 327/310-313, 327/315, 327/316, 330/252, 330/253, 330/254, 330/259, 330/260, 330/291, 330/292
• US Class Current: 327/563
• CPC Class Codes: H03D 2200/0043 Bias and operating point
• CPC Class Codes: H03D 7/1433 using bipolar transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1441 using field-effect transistors H03D7/145 takes precedence
• CPC Class Codes: H03D 7/1458 Double balanced arrangements, i.e. where both input signals are differential
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• 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 3/45071 with semiconductor devices only

Abstract

The active component (400, 500) of a radio device comprises a first transistor (Q1) and a second transistor (Q2). The differential input of the active component comprises a first input line (RF+) and a second input line (RF−), of which the first input line is coupled to the base of the first transistor (Q1) and the second input line is coupled to the base of the second transistor (Q2). In order to match the input impedance there is cross-feedback (Rfb′) between the first transistor (Q1) and the second transistor (Q2).

Claims

1. An active component of a radio device, comprising:

a first transistor and a second transistor,

a differential input with a first input line and a second input line, of which the first input line is coupled to the base of the first transistor and the second input line is coupled to the base of the second transistor, said differential input having an input impedance; and

a cross-feedback connection between the first transistor a nd the second transistor, said connection further comprising;

a first connection through a first feedback RC circuit from the emitter of said first transistor to the base of said second transistor and a second connection through a second feedback RC circuit from the emitter of said second transistor to the base of said first transistor, wherein the value of said input impedance is directly determined by the characteristics of said cross-feedback connection.

2. An active component according to claim 1, wherein the emitter of the first transistor is coupled to the base of the second transistor, and the emitter of the second transistor is coupled to the base of the first transistor.

3. An active component according to claim 2, wherein the coupling between the emitter of the first transistor and the base of the second transistor comprises a first resistor, and the coupling between the emitter of the second transistor and the base of the first transistor comprises a second resistor with a resistance equalling the resistance of the first resistor.

4. An active component according to claim 3, wherein the coupling between the emitter of the first transistor and the base of the second transistor further comprises a first capacitor which is connected in series with the first resistor, and the coupling between the emitter of the second transistor and the base of the first transistor further comprises a second capacitor which is connected in series with the second resistor.

5. An active component according to claim 1, characterized in that it is an amplifier.

6. An active component according to claim 1, characterized in that it is a mixer.

7. A radio device comprising:

a differential active component with a first transistor and a second transistor,

a differential input to the differential active component with a certain input impedance, a first input line and a second input line, of which the first input line is coupled to the base of the first transistor and the second input line is coupled to the base of the second transistor,

an other component in front of the differential active component in the signal propagation direction,

a differential output from the other component with a certain output impedance, and

a cross-feedback connection between the first transistor and the second transistor in the differential active component, said connection further comprising;

a first connection through a first feedback RC circuit from the emitter of said first transistor to the base of said second transistor and a second connection through a second feedback RC circuit from the emitter of said second transistor to the base of said first transistor, wherein the value of said input impedance is directly determined by the characteristics of said cross-feedback connection, in order to match the input impedance of the differential input so that it corresponds to the output impedance of the differential output.

8. A radio device according to claim 7, wherein order to form the cross-feedback the emitter of the first transistor is coupled to the base of the second transistor and the emitter of the second transistor is coupled to the base of the first transistor.

9. A radio device according to claim 7, wherein the differential active component is an amplifier and the component in front of it in the signal propagation direction is a filter.

10. A radio device according to claim 7, wherein the differential active component is a mixer and the component in front of it in the signal propagation direction is an amplifier.