Hi all.


Is it normal for the supply of U3 not implementing a RF choke coil ?
If there was one -say 1mH- Would that be a minimum value that can be made larger ?

To make the circuit operate on 3V instead of 12V; if U3, U4 can work at 3V by their data sheets, changing R10 and R11 to lower values that achieve the same current would be the way to do it or there is more to consider ?

If the antenna is just a piece of random wire of unknown impedance, should C30, L1, C25, C26, C31 values be revised ?

[It is a vhf receiver]

 

Both the AG102 and the SA602A require a minimum voltage of 4.5 volts.

 

Thanks, Ylli. Yes, I know am pushing it. But if those components can work or replaced with 3V equivalent ones; what are the guidelines to make it work on a lower supply voltage ?

AG102 :


Other balanced mixer :

 

Can only speak to the MMICs. These are usually biased in a manner similar to the way you bias an LED. You user the nominal device voltage, the supply voltage, and the device current to determine that series resistor. In this case, I see 12 volt source, 4.5 volts across device, and 70 mA current required. I would have made the resistor (12 - 4.5)/0.07 = 107 ohms. I would have used a 110 ohm.

Using less current than the device is spec'd at results mostly in a degraded IIP3 point, and of course changes in the S parameters.

Trying to simply apply a voltage to the device will result in an unpredictable current and therefore unpredictable S parameters. Makes matching difficult.