运放+三极管组成的恒流源

Analog Engineer's Circuit

Voltage-to-current (V-I) converter circuit with BJT

Amplifiers

Design Goals

Input Output Supply

V

iMin

V

iMax

I

iMax

I

ee

V

load

0V 10V 200µA 0A 1A 15V 0V 36V

Design Description

Design Notes

1. Resistor divider (R1 and R2) is implemented to limit the maximum voltage at the non-inverting input, V

in+

,

and sense resistor, R

5

, at full-scale.

2. For an op amp that is not rail-to-rail input (RRI), a voltage divider may be needed to reduce the input voltage

to be within the common-mode voltage of the op amp.

capacitance of the bipolar junction transistor (BJT), R

4

provides a DC feedback path directly at the current-

setting resistor (R

5

1

provides a high-frequency feedback path that bypasses the BJT.

6. Use the op amp in a linear operating region. Linear output swing is usually specified under the A

OL

test

conditions in the device data sheet.