I need to produce an extremely low noise SPDT switch. This switch will take two different inputs to a single 16 bit ADC. The inputs are 50 ohm BNC outputs from trans-impedance amplifiers. The amplifiers take a small current and convert them to 0-10V DC (they operate between 200 KHz and several MHz). This signal is then sampled at a rate of 1 MHz to 80 MHz, depending on application.
Currently I use the following component:
I tried to design a simple PCB using an OMRON relay. However, this introduced significant baseline voltage as well as noise (100-250 mV plus noise).
Does anyone have any ideas on how to design such a circuit? I tried some off-the-shelf RF switch ICs demo boards but nothing handles DC and/or they clipped at VCC = 3.3V and I need transmission to the full 10V range.
Is there something special about getting a board built at 50 Ohm controlled impedance? I used a single IC to power the relay and a 7805 regulator to provide 5V (the ground is shared with the SMA connectors and power supply).