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Level Controlled AC Clamp

IP.com Disclosure Number: IPCOM000095778D
Original Publication Date: 1964-Jun-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Gruodis, AJ: AUTHOR

Abstract

This is a clamp circuit in which the clamping transistor is continually influenced to remain in saturation regardless of input signal variations.

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Level Controlled AC Clamp

This is a clamp circuit in which the clamping transistor is continually influenced to remain in saturation regardless of input signal variations.

Transistor T1 acts as the clamping device and transistor T2, in combination with Zener diode Z, provides the clamp controlling function. When the control input is at a down level, T2 is nonconductive and causes a high back bias to be placed across Z. This causes a large current to flow from +V to -V. Thus, the emitter of T1 is held at a sufficiently high positive potential so that it is also nonconductive. At this time, the clamp circuit has no affect on the signal line.

When the control input rises to its high level, it supplies a constant current through resistor R1 and diode D1 to render T2 conductive. The resulting voltage drop at the collector of T2 in combination with the input current to the base of T1 from the control input causes T1 to become saturated and clamp the signal line.

If the potential on the signal line tends to rise, an increment of current is forced down through T1 causing the voltage across emitter resistor R2 to incrementally increase. Since the base of T1 remains at a constant potential, the net result is a small decrease in the base current supplied to T1. Due to the fact that the control input in combination with R1 supplies a constant current, the lessening of the base current in T1 causes a current diversion into the base of T2.

This results in an increased collecto...