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ADA4870 low output impedance

Question asked by tripprfs on Mar 21, 2017
Latest reply on Mar 24, 2017 by tripprfs

We are running an EVAL-ADA4870 with the gain resistors set to 1.2kOhm and 130 Ohm for a gain of 10.2, and we have shorted out the resistor on the output of the amplifier for a low impedance path to our circuit. Our circuit is simply an RLC resonator, where the major source of resistance is the amplifier itself. We are running around 35-50 Mhz (46Mhz in particular but we have done 30MHz before). Our circuit seems limited in the voltage it can produce on the LC side by the output impedance of the amplifier being ~4 Ohm @ 30 MHz and 7.5 Ohm at 46MHz, this lowers the Q of the RLC resonator which limits our voltage. The voltage is also limited by the current limit of the ADA4870. I was wondering if there is perhaps a bettter way to set the board of for a lower output impedance, or failing that if there is another product you know of more suited to this purpose (either a lower output impedance at ~45 MHz) or a higher output current. We only need about a factor of 1.5-2 better (either higher current or lower output impedance). 

 

Thank you,

Robert

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