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Voltage Regulation with High Accuracy Reference

IP.com Disclosure Number: IPCOM000085708D
Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Gillingham, RD: AUTHOR [+3]

Abstract

Voltage-reference circuit 10 produces an accurate and stable fixed voltage Vref for series-regulator circuit 20, which in turn provides a fixed supply voltage at high current to load 30.

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Voltage Regulation with High Accuracy Reference

Voltage-reference circuit 10 produces an accurate and stable fixed voltage Vref for series-regulator circuit 20, which in turn provides a fixed supply voltage at high current to load 30.

In circuit 10, the output Vref of open-loop operational amplifier 11 is fed to Zener diode D11 and resistor R11, which is returned to ground point G2 in a physical package which holds circuits 10 and 20. Resistor R12, transistor Q11 and current source 111 form an emitter-follower controlled by the voltage drop Vz across diode D11, and coupled to inverting input 12 of amplifier 11. Vref is also introduced into noninverting input 13 through resistive divider R13, R14.

Closed-loop action of high-gain amplifier 11 requires that V12 = V13, so that: Vref = (1 + R14/R13)(Vz + Vbe) where Vbe is the base-emitter voltage of Q11.

It is well known that the temperature coefficients of a Zener diode and Vbe for a silicon transistor are almost exactly equal and opposite. It is also known that resistor temperature coefficients may be made to track very closely, by fabricating them from the same material and in close proximity on the same substrate. Accordingly, Vref is very nearly constant over temperature and time. If these resistors are screened, R14 may be actively trimmed, so that Vref may also be set to a desired value very accurately.

In regulator 20, Vref is divided by resistors R21 and R22 in the same ratio as the regulator output voltage on sense line 21 is divided by resistors R23 and R24. Sense line 21 is connected close to load 30 to eliminate the effects of the inherent resistance R31 of supply line 31. The lower ends of resistors...