EC5912 datasheet(6/10 Pages) E-CMOS

6 / 10 page

200MHz, CMOS, Rail-to-Rail

Output Operational Amplifier

EC5912

E-CMOS Corp. (www.ecmos.com.tw)

3L18N-Rev.P001

Page 6 of 10

The bigger the RISO resistor value, the more stable VOUT will be. However, if there is

a resistive load RL in parallel with the capacitive load, a voltage divider (proportional to

RISO/RL) is formed, this will result in a gain error. The circuit in Figure 2 is an improvement to the

one in Figure 1. RF provides the DC accuracy by feed-forward the VIN to RL. CF and RISO serve

to counteract the loss of phase margin by feeding the high frequency component

of the output

signal

back to the amplifier’s inverting input, thereby preserving the phase margin in

the overall feedback loop. Capacitive drive can be increased by increasing the value of CF.

This in turn will slow down the pulse response.

Differential amplifier

The differential amplifier allows the subtraction of two input voltages or cancellation of a

signal common the two inputs. It is useful asa computational amplifier in making a differential

To single-end conversion or in rejecting a common mode signal. Figure 3 shown the differential

amplifier using EC5912

If the resistor ratios are equal (i.e. R1=R3 and R2=R4), then

Instrumentation Amplifier

The input impedance of the previous differential amplifier is set by the resistors R1, R2, R3, and R4.

To maintain the high input impedance, one can use a voltage follower in front of each input

as shown in the following two instrumentation amplifiers.

Three-Op-Amp Instrumentation Amplifier

The triple EC5912 can be used to build a three-op-amp instrumentation

amplifier

shown in Figure 4. The amplifier in Figure 4 is a high input impedance

differential

amplifier

with

gain

of R2/R1. The two

differential

voltage

followers assure the high input impedance of the

amplifier.

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