Overdrive thermal distortion compensation for a Quinn cascomp amplifier

• US 4,528,517 A
• Filed: 02/07/1983
• Issued: 07/09/1985
• Est. Priority Date: 02/07/1983
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Tektronix Incorporated (Fortive Corp.)
• Inventors: Schlotzhauer, Kenneth G.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US06/464,795
• Time in Patent Office: 883 Days
• Field of Search: 330/151, 330/256, 330/258, 330/260, 330/261, 330/311
• US Class Current: 330/256
• CPC Class Codes: H03F 1/3211 in differential amplifiers
• CPC Class Codes: H03F 2203/45008 the addition of two signals being made by a resistor addition circuit for producing the common mode signal
• CPC Class Codes: H03F 2203/45018 the differential amplifier amplifying transistors have added cross couplings
• CPC Class Codes: H03F 2203/45024 the differential amplifier amplifying transistors are cascode coupled transistors
• CPC Class Codes: H03F 2203/45052 the cascode stage of the cascode differential amplifier being controlled by a controlling signal, which controlling signal can also be the input signal
• CPC Class Codes: H03F 2203/45086 the common mode signal being taken or deducted from the tail circuit of the differential amplifier
• CPC Class Codes: H03F 2203/45088 the resulting deducted common mode signal being added to or controls the differential amplifier, and being a voltage signal
• CPC Class Codes: H03F 2203/45202 the differential amplifier contains only resistors in the load
• CPC Class Codes: H03F 2203/45212 the differential amplifier being designed to have a reduced offset
• CPC Class Codes: H03F 2203/45471 the CSC comprising one or more extra current sources
• CPC Class Codes: H03F 3/45103 Non-folded cascode stages
• CPC Class Codes: H03F 3/45587 Controlling the active amplifying circuit of the differential amplifier

Abstract

The cascomp amplifier is modified to provide a dynamic biasing circuit which varies the bias point of the cascomp amplifier in proportion to the change in the true bias point of the main channel pair to allow full thermal V_be error correction for overdrive conditions and for common-mode signals. A buffer amplifier senses the average voltage of the main channel input transistor emitters and generates a voltage proportional to this average which is added to the biasing network for the cascomp amplifier common-base amplifier transistors.

Claims

1. A cascomp amplifier, comprising:

a main amplifier comprising an emitter-coupled pair of transistors for converting an input signal to a differential signal current;

a common-base amplifier stage coupled to said main amplifier, said common-base amplifier stage comprising a pair of transistors through which said differential signal current passes;

a correction amplifier having a pair of inputs coupled between said main amplifier and said common-base amplifier stage, and a pair of outputs cross-coupled in a current-aiding sense with the outputs of said common-base amplifier;

a buffer amplifier having an input connected to the junction of a pair of equal-valued resistors coupled between the emitters of said emitter-coupled pair of transistors in said main amplifier to sense the average voltage value therebetween;

voltage divider means for receiving said average voltage value and producing a proportional voltage value of said average voltage value; and

an emitter-follower stage having an input coupled to said voltage divider means and an output coupled to the bases of said pair of transistors comprising said common-base amplifier stage.