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Transistor Pulse Amplifier Circuit

IP.com Disclosure Number: IPCOM000097368D
Original Publication Date: 1962-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Crawford, DJ: AUTHOR [+2]

Abstract

To make high-speed core driver circuits, it is sometimes desirable to use two or more higher speed transistors in parallel to drive the load rather than use a more powerful, but slower, transistor. When two transistors are used in parallel it is difficult for them to share the load equally unless their parameters are identical. The transistor amplifier circuit utilizes a transformer to perform almost perfect load sharing.

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Transistor Pulse Amplifier Circuit

To make high-speed core driver circuits, it is sometimes desirable to use two or more higher speed transistors in parallel to drive the load rather than use a more powerful, but slower, transistor. When two transistors are used in parallel it is difficult for them to share the load equally unless their parameters are identical. The transistor amplifier circuit utilizes a transformer to perform almost perfect load sharing.

The emitter follower output stages are shown with transistors T1 and T2 in parallel to share the load R. If the transistors are identical, I1 and 12 are equal. The net flux produced by these currents in the transformer is zero and no drop or loss in power occurs in the transformer. However, should T1 be faster or have more gain than T2, I1 tends to be greater than 12. This produces a positive voltage at point A with respect to the transformer center tap. Point B is forced negative with respect to the center tap due to the action of the transformer. The overall result is that T1 gets less drive due to the degenerative action of point A rising toward the input drive. Transistor T2 receives more net drive because the emitter is being driven with respect to the base.

Other circuit configurations are possible. A circuit with the transformer and a load in the collector circuit realizes similar results. In this alternative, the stronger transistor tends to go into saturation or bottom, if the weaker transistor is not ...