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Temperature Compensated Clamp

IP.com Disclosure Number: IPCOM000097107D
Original Publication Date: 1962-May-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Valentine, AG: AUTHOR

Abstract

When transistor Q is nonconducting, current flows through resistor R1, diode D1 and resistor R3. R1 and R3 are selected so that currents of equal magnitude flow through diodes D1 and D2. D1 and D2 are selected so that the voltage drop across each is substantially identical. Thus, point X is clamped at voltage V3 plus the voltage drop across D2. Terminal A, under these conditions, is clamped at voltage V3 because the voltage drops across D1 and D2 cancel each other.

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Temperature Compensated Clamp

When transistor Q is nonconducting, current flows through resistor R1, diode D1 and resistor R3. R1 and R3 are selected so that currents of equal magnitude flow through diodes D1 and D2. D1 and D2 are selected so that the voltage drop across each is substantially identical. Thus, point X is clamped at voltage V3 plus the voltage drop across D2. Terminal A, under these conditions, is clamped at voltage V3 because the voltage drops across D1 and D2 cancel each other.

When Q is switched on, current flows through resistor R4, diode D4, R2 and Q as well as R1 and R2 and Q. R1, R2 and R4 are selected so that currents of equal magnitude flow through the D3 and D4 producing equal voltage drops across the same. Now, terminal A is clamped at the voltage V2.

Any voltage drift with temperature of D1 is cancelled by similar voltage drift in D2. Likewise, any voltage drift with temperature of D3 is cancelled by a similar voltage drift in D4.

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