EL2357C 데이터 시트보기 (PDF) - Elantec -> Intersil

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EL2357C

125 MHz Single Supply, Clamping Op Amps

Elantec -> Intersil 

EL2257C/EL2357C

125 MHz Single Supply, Clamping Op Amps

Unlike amplifiers that clamp at the input and are there-

fore limited to non-inverting applications only, the

EL2257C/EL2357C output clamp architecture works for

both inverting and non-inverting gain applications.

There is also no maximum voltage difference limitation

between VIN and VCLAMP which is common on input

clamped architectures.

The voltage clamp operates for any voltage between

+1.2V above the GND pin, and the minimum output

voltage swing, VOP. Forcing the CLAMP pin much

below +1.2V can saturate transistors and should there-

fore be avoided. Forcing the CLAMP pin above VOP

simply de-activates the CLAMP feature. In other words,

one cannot expect to clamp any voltage higher than what

the EL2257C/EL2357C can drive to in the first place. If

the clamp feature is not desired, either let the CLAMP

pin float or connect it to the VS+ pin.

EL2257C/EL2357C Comparator Application

The EL2257C/EL2357C can be used as a very fast, sin-

gle supply comparator by utilizing the clamp feature.

Most op amps used as comparators allow only slow

speed operation because of output saturation issues.

However, by applying a DC voltage to the CLAMP pin

of the EL2257C/EL2357C, the maximum output voltage

can be clamped, thus preventing saturation. Figure 4 is

amplifier A of an EL2257C implemented as a compara-

tor. 2.25V DC is applied to the CLAMP pin, as well as

the IN- pin. A differential signal is then applied between

the inputs. Figure 5 shows the output square wave that

results when a ±1V, 10 MHz triangular wave is applied,

while Figure 6 is a graph of propagation delay vs. over-

drive as a square wave is presented at the input.

Figure 4.

Figure 5.

Propagation Delay vs Overdrive

EL2257/EL2357 as a Comparator

Figure 6.

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