My purpose is to amplify the current signal generated by APD into a voltage signal through a two-stage amplifier. The first stage amplifier is going to use ltc6268-10 to amplify the current signal into a voltage signal, and the second stage amplifier is going to use AD8336 to further amplify the voltage signal output by ltc6268-10.
My question is how to couple ltc6268-10 and AD8336. Is it possible to connect ltc6268-10 and AD8336 directly?
The LTC6268-10 output from your APD 1st stage would be capable of driving the INPP input of the AD8336 directly (DC or AC coupled if a bias current path is provided). If you keep the distance between the two stages on the board short enough relatively to the 150MHz capability of the AD8336, you can directly connect these two stages with no termination required. Having a place-holder for a low value (< 50ohm) resistor in series with the signal path may be useful to be able to tune the response if need be.
Hope this answers your question?