Differential amplifiers

A differential amplifier comprises two transistors (T1 and T2) having their collectors connected through respective loads (R1 and R2) to one supply line VL1, their emitters connected together and to a controllable constant current source (IB) which supplies a bias current (Ib) and which is connected...

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Bibliographic Details
Main Author CHAPMAN, DAVID MARK
Format Patent
LanguageEnglish
French
German
Published 19.09.1990
Subjects
AMPLIFIERS
BASIC ELECTRONIC CIRCUITRY
ELECTRIC COMMUNICATION TECHNIQUE
ELECTRICITY
PICTORIAL COMMUNICATION, e.g. TELEVISION
PULSE TECHNIQUE
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Summary:A differential amplifier comprises two transistors (T1 and T2) having their collectors connected through respective loads (R1 and R2) to one supply line VL1, their emitters connected together and to a controllable constant current source (IB) which supplies a bias current (Ib) and which is connected between the common connection of the emitters and a return supply line (VL2). The transistor bases are connected to receive a control voltage (Vc). The common connection of the emitters is also connected through a by-pass resistance (RB) to a bias voltage source (+VB). The circuit parameters are such that flow of bias current (Ib) will result in a small current (Ir) being diverted through the by-pass resistance (RB) instead of flowing through the transistors. This small current approximates in value to the value of any residual bias current when the current source (IB) is switched off, but has a value which is negligible relative to the value of the bias current when the current source (IB) is switched on.
Bibliography:Application Number: EP19900200517