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Reference Voltage Circuit

IP.com Disclosure Number: IPCOM000091189D
Original Publication Date: 1969-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Chang, DC: AUTHOR

Abstract

A constant voltage device such as a zener diode has a finite zener resistance. Under a wide input current condition its terminal voltage change becomes excessive. This circuit cooperates with a constant voltage device to yield a superior voltage-current characteristic and higher power handling capacity.

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Reference Voltage Circuit

A constant voltage device such as a zener diode has a finite zener resistance. Under a wide input current condition its terminal voltage change becomes excessive. This circuit cooperates with a constant voltage device to yield a superior voltage-current characteristic and higher power handling capacity.

Zener diode 1 is in series with resistor 2. Transistor 3 is connected between diode 1 and resistor 2 and in parallel with them. Load resistor 4 is connected in the collector circuit of transistor 3. Transistor 3 can be a multidevice amplifier such as a Darlington emitter-follower.

Input current Iin flows through diode 1 and resistor 2 to a certain value iR until the voltage drop across resistor 2 reaches the turn on point of transistor 3. A large part of the input current is shunted by transistor 3. Diode 1 experiences only a small current change. The amount of this current change is the input current divided by the current gain of transistor 3. The effect is to reduce the zener voltage variation. Resistor 4 acts with transistor 3 to share in the dissipation of input power. Its resistance is sufficiently small such that the voltage drop from the maximum current is less than the reference voltage and the transistor is maintained in a nonsaturated state. The effect of this circuit arrangement as contrasted with the use of a zener diode alone is shown in the current voltage characteristic.

The circuit arrangement has the advantage of increas...