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# Symmetry Regulating Circuit

IP.com Disclosure Number: IPCOM000091423D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 38K

IBM

## Related People

Esteban, D: AUTHOR [+2]

## Abstract

When it is desirable to derive from a two-terminal voltage source two voltage sources having the same voltage and a very low dynamic impedance, two zener diodes connected in series with the supply voltage can be used. In this case, the two voltage sources are derived across each diode whose characteristics must closely match one another. However, this method provides only fairly good results. Another circuit can be used where zener diodes are replaced by transistors and resistors, forming a high-gain operational amplifier.

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Symmetry Regulating Circuit

When it is desirable to derive from a two-terminal voltage source two voltage sources having the same voltage and a very low dynamic impedance, two zener diodes connected in series with the supply voltage can be used. In this case, the two voltage sources are derived across each diode whose characteristics must closely match one another. However, this method provides only fairly good results. Another circuit can be used where zener diodes are replaced by transistors and resistors, forming a high-gain operational amplifier.

The supply voltage is applied between terminals +U and -U so that a DC feeds two load resistors RL and RL' across which the output voltages +Vo and - Vo respectively are developed. A portion of supply voltage is derived from common point A of resistors R1 and R2 connected between the supply voltage terminals +U and -U and is compared with a portion of -Vo that is derived from common point A' of resistors R'1 and R'2 connected in parallel with RL'. The difference in the voltage values at points A and A' is detected in the long-tail pair formed by transistors T1 and T2. The output signal of this differential amplifier is amplified by transistors T3 and T4 whose load is a resistor of low value connected to supply voltage terminal -U. The main function of T3 and T4 is to drain a fraction of DC circulating in RL from circulating in RL'. An additional requirement for the correct operation of this circuit is that the value of RL' be greater than that of RL.

Assuming that common point B of RL and RL' is disconnected from the output terminal of the operational amplifier, then -Vo developed across RL' is greater than +Vo. When point B is connected to the output of the operatio...