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ADL5565 gain accuracy, overdrive

Question asked by Nanoman on Jan 7, 2013
Latest reply on Jan 9, 2013 by Nanoman

Hi

 

I have inherited a former colleagues design and need to report on it's performance. It uses two ADL5565 amplifiers to provide gain and drive to an ADC. I have read the datasheet and have some concerns.

 

Gain accuracy

The datasheet states +/-1dB gain accuracy (+/- 12%) which I assume is resistor mismatch. The circuit is designed to have 50R input impedance to match the source, the internal resistors play a significant part of this. The circuit adjusts the input dc level using external 470R resistors and this would also be affected by the values of Rg1, Rg2 etc.

I could assume the values change neatly around the nominal value but actual values would help.

 

High frequency overdrive

The circuit is designed to amplify signals in the region of 20mVpk but could encounter signals up to 1.5Vpk. The application is for DC to 1GHz signals but users could put faster signals in. Looking at the absolute maximum ratings (page 9) there's a good chance we'll exceed the 2000Vpp MHz limit.

I'll assume this is unacceptable and the input requires clamping?

 

Will a spice model be available for this device? I'm using a standard part to check that input common mode voltage and output current is within spec but it's unlikely overload behaviour will match.

 

Regards

 

Lee

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