AD600: Distortion of the output waveform

Document created by analog-archivist Employee on Feb 23, 2016
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My customer using the standard electrical scheme showed on the
datasheet see a distortion of the output waveform (from sinusoidal input
they see a triangular output).
Condition are:

INPUT:         2Vpp  Sinusoidal
          1Mhz bandwith

Gain: 0dB

Output         Triangular waveform

Seem to be a problem on the slewrate of the input stage, this is also
confirmed reducing the input voltage range.

 

The AD600 has an output slew rate of 275V/us. To calculate the full power
bandwidth use:
FPBW = Slew_Rate / [2 x PI x Vpeak ]

For the AD600 with a 5V minimum output swing, the Full Power Bandwidth is
275000000 / [ 2x PI x 2.5 ] = 17.5MHz.

Therefore the AD600 is not slew rate limited by a 1MHz 2V peak to peak output
signal. The maximum nominal input for the AD600 is 1V rms or 2.8Vpeak to peak,
therefore you are also within the expected input range

One thing that users of the AD600 often over look is the low input impedance of
nominally 100Ohms. To drive 2V signal into 100 ohms requires a source which can
output 20mA and maintain distortion performance. Ask your customer to check the
signal on the input pin A1HI and ensure that it is pure sine wave. If it is not
then the input of the AD600 is loading the signal source and a buffer is
required.

Also check the loading on the output of the AD600, the load should not be
smaller than 500ohms assuming an output signal of +/-2.5V.

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