[time-nuts] ? phase comparison or other device
Dr Bruce Griffiths
bruce.griffiths at xtra.co.nz
Sun Jul 1 19:01:10 EDT 2007
Bob Paddock wrote:
> "The AD8036 and AD8037, from Analog Devices, are wide bandwidth, low distortion clamping amplifiers.
> The AD8036 is unity gain stable. The AD8037 is stable at a gain of two or greater.
> These devices allow the designer to specify a high (VCH) and low (VCL) output clamp voltage.
> The output signal will clamp at these specified levels."
> AN-402: Replacing Output Clamping Op Amps with Input Clamping Amps (pdf, 57,313 bytes)
> "So far most clamping amplifiers have relied upon an output clamping architecture and are called output clamp amps (OCAs).
> A new architecture called an input clamp amp (ICA) offers superior clamping accuracy and lower distortion."
A significant issue with these clamping amplifiers is that although when
the clamp is active the signal gain is near very low, the amplifier
noise gain is the same as when the clamp isn't active.
In contrast with a simple diode clamp, the signal gain is low when the
clamp is conducting and the amplifier noise gain is at worst unity.
Surely this characteristic of a simple diode clamp reduces the noise
associated with the amplifier accumulated on the low pass filter
capacitor in a zero-crossing detector over the amplifier noise
contribution from an equivalent zero-crossing detector using such input
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