LMP7715MFSLASHNOPB datasheet(18/27 Pages) TI

18 / 27 page

10 k:

VIN

VOUT

= 1 +

VOUT

VIN = KI

IR RADIATION

INTENSITY, I

THERMOPILE

VOUT RA

K(RA + RB)

I =

LMP7715, LMP7716, LMP7716Q

SNOSAV0E – MARCH 2006 – REVISED MARCH 2013

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Figure 56. Thermopile Sensor Interface

PRECISION RECTIFIER

Rectifiers are electrical circuits used for converting AC signals to DC signals. Figure 57 shows a full-wave

precision rectifier. Each operational amplifier used in this circuit has a diode on its output. This means for the

diodes to conduct, the output of the amplifier needs to be positive with respect to ground. If VIN is in its positive

half cycle then only the output of the bottom amplifier will be positive. As a result, the diode on the output of the

bottom amplifier will conduct and the signal will show at the output of the circuit. If VIN is in its negative half cycle

then the output of the top amplifier will be positive, resulting in the diode on the output of the top amplifier

conducting and delivering the signal from the amplifier's output to the circuit's output.

For R2/ R1 ≥ 2, the resistor values can be found by using the equation shown in Figure 57. If R2/ R1 = 1, then R3

should be left open, no resistor needed, and R4 should simply be shorted.

Figure 57. Precision Rectifier

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LMP7715MF/NOPB 데이터시트(PDF) 18 Page - Texas Instruments