AD8036: need clarification on "fast rectifier" use.

First a disclaimer, I'm only a mechanical engineer, doing this out of necessity as a grad student.

I'm hoping to use either AD8036 or AD8037 as a peak detector for a nearly sinusoidal waveform at 100Hz-5MHz. The datasheet gives this handy schematic on page 19 and claims good performance to 20MHz. I am willing to tolerate error of a couple % at high frequency.

However, the same datasheet also says on page 16 (bottom of right column) that "The AD8036's and AD8037's CLAMPIN input clamp architecture works only for noninverting or follower applications..."

Doesn't the schematic show an inverting application?  Is this just an "oops" or is it the correct layout?


Now just a couple of basic questions. My intent is to use a simple RC filter on the output. I am sampling the output at 10Hz so a large time constant is desired. Can I assume that in this case, a relatively large C (0.1uF) does not constitute a problematic capacitive load?

Thanks!

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    •  Analog Employees 
    on Sep 15, 2014 11:16 PM

    Hi Ilya,

    1. The circuit is configured as inverting of gain unity and this is not an error in the datasheet.

    The CLAMPIN circuit only affects the A1's non inverting input. The CLAMPIN is comprised of comparators CH and CL, which drive S1 through a decoder. Considering the circuit, VH left open  and VL is referenced to 2Vin (due to noise gain of 2) and +Vin is grounded, S1 connects positive input of A1 to VL. Please refer on the datasheet page 19 ad 20 further explanation on how the circuit will operate.

    2. With your RC filter on the output, can you provide schematic?

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  • 0
    •  Analog Employees 
    on Sep 15, 2014 11:16 PM

    Hi Ilya,

    1. The circuit is configured as inverting of gain unity and this is not an error in the datasheet.

    The CLAMPIN circuit only affects the A1's non inverting input. The CLAMPIN is comprised of comparators CH and CL, which drive S1 through a decoder. Considering the circuit, VH left open  and VL is referenced to 2Vin (due to noise gain of 2) and +Vin is grounded, S1 connects positive input of A1 to VL. Please refer on the datasheet page 19 ad 20 further explanation on how the circuit will operate.

    2. With your RC filter on the output, can you provide schematic?

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