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Clamping Differential Amplifier

IP.com Disclosure Number: IPCOM000091722D
Original Publication Date: 1968-Apr-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Lutze, W: AUTHOR

Abstract

T1 and T2 form a differential amplifier with inputs I1 and I2. When the element is suitably dimensioned approximately symmetrical emitter currents flow into T1 and T2. Thus, if the emitter base voltage of both transistors is the same, e.g., in the case of an integrated circuit on the same semiconductor ship, the potential difference between I1 and I2 is negligibly small.

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Clamping Differential Amplifier

T1 and T2 form a differential amplifier with inputs I1 and I2. When the element is suitably dimensioned approximately symmetrical emitter currents flow into T1 and T2. Thus, if the emitter base voltage of both transistors is the same, e.g., in the case of an integrated circuit on the same semiconductor ship, the potential difference between I1 and I2 is negligibly small.

A minor change of the base current of T1 or T2 causes an increased collector potential change in the opposite direction of the respective transistor which returns the base-emitter voltage of T1 and T2, via the direct negative feedback, through transistors T3 and T4 to the initial value. At output terminals 01 and 02, an amplified differential signal is available of the input voltage applied at the extremely low-ohmic inputs I1 and 12. The advantages of the circuit are 1. Fully symmetrical negative feedback, 2. Direct negative feedback in the shortest possible way, therefore no tendency of oscillations, even at high frequencies, 3. High clamping effect with fully symmetrical reaction of both inputs, resulting in a very low input resistance of the amplifier, 4. Minimum voltage difference between the input terminals, and 5. Pure current amplification with a very high amplification factor stability.

The amplifier changes the current fed into the input terminal into an output voltage proportional to it and is practically independent of the semiconductor data. This linea...