Question
A customer is using the ADL5511 in an AGC loop application, by applying a sine
wave at different power levels using a signal generator and using the Vrms
output pin to measure the output. They have a 75 Ohm resistor connected
between pin 2 (RFIN) and ground. The circuit is not behaving as it should.
Answer
The RF input needs to be AC-coupled and the 75 Ohm resistor to ground should
not be connected directly to pin 2 (RFIN). They may be pulling down the bias
level on the RF input. The input frequency will determine whether they need
caps on FLT2 and FLT.