Browse Prior Art Database

Transistor Speed Up Circuit

IP.com Disclosure Number: IPCOM000089876D
Original Publication Date: 1968-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Picciano, JK: AUTHOR

Abstract

This circuit uses the excess charge stored in saturated transistor Q2 to supply drive to output transistor 44. Load L is a shorted transmission line which appears to be inductive for required frequencies. Q4 is the positive driver and transistor Q5 the negative driver. If Q4 is turned on rapidly, the voltage at its emitter appears as an exponential whose time constant is determined by inductance L and resistance R3. During the initial period of the exponential, the voltage approaches +VC. At this time it is difficult to obtain sufficient drive into the base of Q4 without making WB excessively large or resistor R1 very small. To overcome this difficulty, transistor Q3 is provided. When transistor Q1 is turned off, collector current for Q1 flows into the base of transistor Q2 and through its collector to Q3.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Transistor Speed Up Circuit

This circuit uses the excess charge stored in saturated transistor Q2 to supply drive to output transistor 44. Load L is a shorted transmission line which appears to be inductive for required frequencies. Q4 is the positive driver and transistor Q5 the negative driver. If Q4 is turned on rapidly, the voltage at its emitter appears as an exponential whose time constant is determined by inductance L and resistance R3. During the initial period of the exponential, the voltage approaches +VC. At this time it is difficult to obtain sufficient drive into the base of Q4 without making WB excessively large or resistor R1 very small. To overcome this difficulty, transistor Q3 is provided. When transistor Q1 is turned off, collector current for Q1 flows into the base of transistor Q2 and through its collector to Q3. Q2 thus saturates and builds up excess charge while acting as an inverse transistor. The base current of Q2 at this time is almost as large as the collector current of Q1 allowing a deep saturation condition to occur. After a length of time determined by the device time constants, Q3 can be turned off. Current now flows through Q2 in the normal direction into the base of Q4, rapidly turning Q4 on.

1

Page 2 of 2

2

[This page contains 1 picture or other non-text object]