Browse Prior Art Database

Darlington Pulldown Clamp

IP.com Disclosure Number: IPCOM000077190D
Original Publication Date: 1972-Jun-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Geller, H: AUTHOR [+2]

Abstract

This circuit is arranged to set a voltage level across the base and emitter of a transistor, such that the base-emitter parasitic capacitance of the transistor is maintained in a charged state. By so maintaining this parasitic capacitor in a charged state the turn-on time of the transistor is minimized.

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

Darlington Pulldown Clamp

This circuit is arranged to set a voltage level across the base and emitter of a transistor, such that the base-emitter parasitic capacitance of the transistor is maintained in a charged state. By so maintaining this parasitic capacitor in a charged state the turn-on time of the transistor is minimized.

When a positive input signal is applied to the bases of the transistors 11 6 12, these devices are turned on. This, in turn, causes the emitters and the bases of transistors 13 and 14 to become coupled to a negative voltage -V applied to the emitters of transistors 11 and 12. This application of a negative voltage to transistors 13 and 14 also causes these transistors to turn off. However, because the emitter of transistor 14 is coupled to transistor 12 via diode 15 while its base is between the emitter and base of transistor 14 a voltage drop of 0.5 volt caused by the added voltage drop of the extra diode. This voltage is sufficient to keep the base-emitter parasitic capacitance of transistor 14 in a charged condition. If a positive signal now is impressed on the base of transistor 14, it will turn on faster since the delay time associated with the charging of the parasitic base- emitter capacitor has been eliminated.

1

Page 2 of 2

2

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