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Parallel Operation of Transistors

IP.com Disclosure Number: IPCOM000083129D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 33K

IBM

Related People

Buhler, OR: AUTHOR

Abstract

In high-power linear amplifiers or series regulators, the need sometime arises for dissipating more power than one transistor can handle. The solution to this problem is to operate two or more transistors in parallel. A major problem, with parallel operation of transistors, is the difference in emitter-base voltage from device-to-device.

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Parallel Operation of Transistors

In high-power linear amplifiers or series regulators, the need sometime arises for dissipating more power than one transistor can handle. The solution to this problem is to operate two or more transistors in parallel. A major problem, with parallel operation of transistors, is the difference in emitter-base voltage from device-to-device.

The device as depicted in Fig. la is a scheme for improving the power dissipation (equalization) of transistor 10 and transistor 12. In the device, matching takes place in the low-current, low-power base circuit rather than the high-current, high-power emitter circuit.

In operation, sensing means 14 and sensing means 16 sense the current outputted from transistors 10 and 12, respectively. The current outputted from sensing means 14 and sensing means 16 are compared by comparator 18 whose output is a differential current.

If the current in transistor 10 is greater than the current in transistro 12, the magnitude and polarity of the output current from comparator 18 is such that the voltage drop across resistor 20 will increase and the voltage drop across resistor 22 will decrease. thus enhancing matching. Conversely, if the current in transistor 12 is greater than the current in transistor 10, the voltage drop across resistor 22 will increase while the voltage drop across resistor 20 will decrease.

A scheme showing the interconnection of three transistors for improving parallel operation is shown...