Class B push-pull differential amplifiers of the single-end output

• US 5,966,050 A
• Filed: 07/09/1998
• Issued: 10/12/1999
• Est. Priority Date: 07/10/1997
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Miura, Sakiko, Yoshino, Hiroshi
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Nguyen, Patricia T.
• Application Number:
  US09/112,507
• Time in Patent Office: 460 Days
• Field of Search: 330/255, 330/257, 330/292, 330/311
• US Class Current: 330/255
• CPC Class Codes: H03F 1/307 in push-pull amplifiers
• 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 2203/45648 the LC comprising two current sources, which are not cascode current sources
• CPC Class Codes: H03F 2203/45696 the LC comprising more than two resistors
• CPC Class Codes: H03F 2203/45708 the LC comprising one SEPP circuit as output stage
• CPC Class Codes: H03F 3/3067 with asymmetrical driving of the end stage
• CPC Class Codes: H03F 3/45085 Long tailed pairs H03F3/45112, H03F3/45139 take precedence
• CPC Class Codes: H03F 3/45094 Folded cascode stages

Abstract

A differential amplifier includes an input differential pair constituted by differential pair transistors whose common emitter is current-biased by a negative voltage source through a constant current source. An active load is formed by interconnecting through resistors input and output of a first and second current mirror circuit whose emitters serve as positive voltage sources. A collector output of each of the input differential pair is connected to each of the outputs of the first and second current mirror circuits. An output current amplifying stage comprises three emitter-grounded current amplifying stages whose emitters serve as positive voltage sources. The first current amplifying stage includes a capacity provided between the base and collector thereof and connected to one of current mirror outputs of the active load at the base thereof. The second and third current amplifying stages are connected to the other current mirror output of the active load at a common base. One of collector outputs thereof is connected to a negative voltage source through a resistor with a capacity provided between the base and collector. The other collector output is connected to the input of a third current mirror circuit whose emitters serve as negative voltage sources.

Claims

1. A differential amplifier comprising:

an input differential pair constituted by differential pair transistors whose common emitter is current-biased by a negative voltage source through a constant current source;

an active load which is formed by interconnecting through resistors input and output of a first and second current mirror circuit constituted by transistors having conductivity opposite to that of said differential pair whose emitters serve as positive voltage sources and in which a collector output of each of said input differential pair is connected to each of the outputs of said first and second current mirror circuits; and

an output current amplifying stage comprising three emitter-grounded current amplifying stages including a first, a second, and a third current amplifying stages which are formed using transistors having the same conductivity as the transistors forming the active load and whose emitters serve as positive voltage sources, the first current amplifying stage including a capacity provided between the base and collector thereof and connected to one of current mirror outputs of said active load at the base thereof, the second and third current amplifying stages being connected to the other current mirror output of said active load at a common base, and each of collectors output, one of collector outputs thereof being connected to a negative voltage source through a resistor with a capacity provided between the base and collector, the other collector output being connected to the input of a third current mirror circuit formed using transistors having the same conductivity as said differential pair transistors whose emitters serve as negative voltage sources, wherein

the output of said third current mirror circuit is connected to the output collector of said first current amplifying stage to provide a single-end output.

2. The differential amplifier according to claim 1, wherein a current mirror circuit as a transfer means is provided between said input differential pair and said active load to provide folding in the circuitry.

3. The differential amplifier according to claim 1, wherein a constant current source as a transfer means is provided between said input differential pair and said active load to provide folding in the circuitry.

4. The differential amplifier according to claim 1, wherein base-grounded transistors as a transfer means are provided between said input differential pair and said active load to provide folding in the form of cascade connection in the circuitry.