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Open Loop Amplifier Configuration Having a "Semiprecise" Voltage Gain

IP.com Disclosure Number: IPCOM000077196D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Swart, DP: AUTHOR [+2]

Abstract

This circuit is capable of providing an accurately defined gain of several hundred without the necessity for feedback at the signal frequency. The input signal is applied to the base of transistor 1. Transistors 1 and 2 are connected in a differential relationship. Since the load seen by transistor 2 is substantially larger than that seen by transistor 1, the gain from the base of transistor 1 to the emitter of transistor 2 is essentially unity. By proper selection of circuit parameters, it is possible to achieve a unity gain from the emitter of transistor 2 to the base of transistor 3. This is accomplished by making the equivalent emitter impedance for transistor 2 equal to the equivalent collector load impedance seen by transistor 2.

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Open Loop Amplifier Configuration Having a "Semiprecise" Voltage Gain

This circuit is capable of providing an accurately defined gain of several hundred without the necessity for feedback at the signal frequency. The input signal is applied to the base of transistor 1. Transistors 1 and 2 are connected in a differential relationship. Since the load seen by transistor 2 is substantially larger than that seen by transistor 1, the gain from the base of transistor 1 to the emitter of transistor 2 is essentially unity. By proper selection of circuit parameters, it is possible to achieve a unity gain from the emitter of transistor 2 to the base of transistor 3. This is accomplished by making the equivalent emitter impedance for transistor 2 equal to the equivalent collector load impedance seen by transistor 2.

The gain of transistor 3, which functions as an inverter, is to defined according to the following expression: G = (RL)/(re3) = (Ie3)(RL)/(0.026) = 40(Vdc). Since the circuit provides unity gain up to the point of base of transistor 3, the actual gain of the entire circuit will be equal to 40(Vdc).

In order to maintain the extreme unbalance between the currents conducted by transistors 1 and 2, it is necessary to hold the voltage at the base of transistor 2 to a value very closely representing that at the base of the input signal to transistor 1. This is accomplished by a noninverting amplifier 4 and storage capacitor 5. The value of capacitor 5 is quite large, t...