US 7,728,667 B2Granted

Differential amplifier

AssigneeYokogawa Electric Corporation

InventorsYoshinobu Sugihara, Satoru Togo

Life of this patent

Estimating the term…

Loading patent…

Abstract

A differential amplifier is constituted of first emitter-follower transistors, second emitter-follower transistors, and amplification transistors whose bases are alternately connected to the emitters of the second emitter-follower transistors and whose collectors are connected to the emitters of the first emitter-follower transistors, as well as emitter resistors and constant current sources, whereby it is possible to reduce distortions of output signals in response to large-amplitude input signals, thus ensuring high-speed operation. It is possible to further incorporate base-grounded transistors and diodes, by which substantially the same collector-emitter voltage is applied to the emitter-follower transistors and amplification transistors, thus achieving the same power consumption and the same temperature variations with respect to these transistors. This reduces the nonlinear amplification error due to temperature differences of transistors, thus achieving flat gain characteristics in broad ranges of frequencies.

Claims10

Dependent claims

A differential amplifier comprising:

a pair of first emitter-follower transistors for buffering input signals;
a pair of voltage drop generation circuits for generating voltage drops dependent upon collector currents at the collectors of the first emitter-follower transistors;
a pair of second emitter-follower transistor for buffering output signals of the first emitter-follower transistors;
a pair of first amplification transistors which are alternately connected with the first emitter-follower transistors and are driven by the second emitter-follower transistors;
a pair of second amplification transistors which are driven by the second emitter-follower transistors, thus providing output signals;
a pair of first base-grounded transistors which are inserted between the first emitter-follower transistors and the first amplification transistors;
a pair of second base-grounded transistors which are inserted between the second amplification transistors and output terminals;
and
a bias circuit for supplying each of the first base-grounded transistors and the second base-grounded transistors with a bias voltage, thus setting a same collector-emitter voltage to each of the first emitter-follower transistors and each of the first amplification transistors and the second amplification transistors.

6 more elements

A differential amplifier comprising:

a pair of first emitter-follower transistors for receiving input signals at bases thereof;
a pair of voltage drop generation circuits for generating voltage drops dependent upon collector currents at the collectors of the first emitter-follower transistors;
a pair of second emitter-follower transistors which are connected with the first emitter-follower transistors;
a pair of first amplification transistors whose bases are alternately connected to emitters of the second emitter-follower transistors and whose collectors are connected to emitters of the first emitter-follower transistors;
a pair of second amplification transistors whose bases are connected to the bases of the first amplification transistors, thus providing output signals;
a pair of first base-grounded transistors inserted between the emitters of the first emitter-follower transistors and the collectors of the first amplification transistors;
a pair of second base-grounded transistors which are connected to collectors of the second amplification transistors;
and
a bias circuit for supplying each of the first base-grounded transistors and the second base-grounded transistors with a bias voltage, thus setting a same collector-emitter voltage to each of the first emitter-follower transistors, each of the first amplification transistors, and each of the second amplification transistors.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/200,450Filed 28 Aug 2008
Priority: JP 2007-22664631 Aug 2007
Published: US 2009/0058522 A15 Mar 2009
Granted: 1 Jun 2010
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

H03F 1/3211
Modifications of amplifiers to reduce non-linear distortion: in differential amplifiers
H03F 3/45085
Using bipolar transistors as the active amplifying circuit: long tailed pairs
H03F 3/45089
Long tailed pairs: non-folded cascode stages
H03F 3/45484
Characterised by the way of common mode signal rejection: in differential amplifiers with bipolar transistors as the active amplifying circuit