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Level Shift Circuit

IP.com Disclosure Number: IPCOM000086901D
Original Publication Date: 1976-Nov-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Heuber, K: AUTHOR [+4]

Abstract

This level-shift circuit utilizes the perfect tracking presented by identically designed and oriented resistors and transistors driven by the same current and incorporated in monolithically integrated circuits.

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Level Shift Circuit

This level-shift circuit utilizes the perfect tracking presented by identically designed and oriented resistors and transistors driven by the same current and incorporated in monolithically integrated circuits.

The level-shift circuit consists of input transistor T1 whose emitter potential is VBB = -2V and of two output driver transistors T5 and T6 whose emitter potential is VEE = -SV. Current is fed to diode T3 by way of resistor R3. Transistor T4 carries a collector current which exactly corresponds to the current flowing through resistor R3. The base current of NPN transistors T5 and T6 can be neglected because of the high current amplification.

When input transistor T1 is on, voltage VBB +0.2V (0.2 V is the assumed saturation voltage across T1) is applied to the base of transistor T2. Resistor R4 has the same volume as resistor R3. This means that the base of transistor T2 is subjected to the same voltage as resistor R3. Transistors T5 and T6 are nonconductive. This state is independent of the differential voltage between VBB and VEE, since transistors T3 and T4 are identical and the currents through resistors R3 and R4 change by about the same amount when the differential voltage changes. The temperature dependence of the base-emitter voltages and of the resistors do not affect the function of the circuit either. The influences in both circuit branches R3, T3 and T2, R4, T4 compensate each other completely.

When input transistor T1 is non...