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Amplifier

IP.com Disclosure Number: IPCOM000096650D
Original Publication Date: 1963-Sep-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Harper, LR: AUTHOR

Abstract

This amplifier has an input stage 1 and an intermediate stage 2. Also, the output stage has power transistors 3 and 4 and a monitoring circuit having transistor 5 and current monitoring resistor 6.

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Amplifier

This amplifier has an input stage 1 and an intermediate stage 2. Also, the output stage has power transistors 3 and 4 and a monitoring circuit having transistor 5 and current monitoring resistor 6.

As a negative-going signal is applied from input terminal 7 to transistor 1, transistor 3 is biased toward cutoff, reducing the current flowing through resistor
6. This action reduces the current flow through transistor 5 which causes the emitter of transistor 4 to draw more current. A positive input signal turns on transistor 3, increasing the voltage across resistor 6 and the current flow through transistor 5. This results in transistor 4 being cut off.

If the load current to output terminal 8 exceeds the current through resistor 6, silicon power diode 9 limits the voltage across resistor 6 to a safe level. This prevents damage to transistor 5 and permits higher transient current to the load. Thus, the monitoring circuit of the amplifier controls the idling current. Such effectively prevents extremes of cross-over distortion, when the bias is too high, or thermal runaway when the bias is too low.

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