-

+

LMP201X

+Input

-Input

(0V to 5V Range)

430:

LM9140-2.5

+2.5V

+5V

ADC1203X

+VREF

GND

-VREF

VIN

+5V

1M

C4

0.01

PF

1N4731A

(4.3V)

D1

7

2

6

4

3

Input

-15V

R6

10k

(-0.7V)

-

+

R1

R7, 3.9k

R2

C2

3

2

6

7

4

LMP201X

U1

LM6171

U2

+

-

R5, 1M

(+2.5V)

Output

C5

0.01 PF

+15V

R4

3.9k

R3

20k

D2

1N4148

C3

0.01 PF

+15V

LMP2012QML

SNOSAU5H – MARCH 2007 – REVISED APRIL 2013

www.ti.com

Table 2. Composite Amplifier Measured Performance

AV

R1

R2

C2

BW

SR

en p-p

Ω

Ω

pF

MHz

(V/

μs)

(mVPP)

50

200

10k

8

3.3

178

37

100

100

10k

10

2.5

174

70

100

1k

100k

0.67

3.1

170

70

500

200

100k

1.75

1.4

96

250

1000

100

100k

2.2

0.98

64

400

In terms of the measured output peak-to-peak noise, the following relationship holds between output noise

voltage, en p-p, for different closed-loop gain, AV, settings, where −3 dB Bandwidth is BW:

Figure 7.

It should be kept in mind that in order to minimize the output noise voltage for a given closed-loop gain setting,

one could minimize the overall bandwidth. As can be seen from Equation 1 above, the output noise has a

square-root relationship to the Bandwidth.

In the case of the inverting configuration, it is also possible to increase the input impedance of the overall

amplifier, by raising the value of R1, without having to increase the feed-back resistor, R2, to impractical values,

by utilizing a "Tee" network as feedback. See the LMC6442 data sheet (Application Notes section) for more

details on this.

Figure 8.

10

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