PLMP7704HBHSLASHEM datasheet(21/31 Pages) TI

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7.4 Device Functional Modes

7.4.1 Precision Current Source

The LMP7704-SP can each be used as a precision current source in many different applications. Figure 7-6

shows a typical precision current source. This circuit implements a precision voltage controlled current source.

Amplifier A1 is a differential amplifier that uses the voltage drop across RS as the feedback signal. Amplifier A2 is

a buffer that eliminates the error current from the load side of the RS resistor that would flow in the feedback

resistor if it were connected to the load side of the RS resistor. In general, the circuit is stable as long as the

closed loop bandwidth of amplifier A2 is greater then the closed loop bandwidth of amplifier A1. If A1 and A2 are

the same type of amplifiers, then the feedback around A1 will reduce its bandwidth compared to A2.

LOAD

I = (V2 ± V1)

Figure 7-6. Precision Current Source

The equation for output current can be derived as shown in Equation 4.

V2R

R + R

(V0 ± IRS)R

V1R

V0R

R + R

(4)

Solving for the current I results in the Equation 5.

I =

± V1

(5)

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LMP7704-SP

SNOSDB6A – DECEMBER 2020 – REVISED JANUARY 2021

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PLMP7704HBH/EM Datasheet(PDF) 21 Page - Texas Instruments