RF Circuits

Here's an interesting S-AV10H TOSHIBA RF Power Amplifier Module circuit. It can deliver over 14W with as low as 100-200mW input power. The system is tuned for 50 ohm input and output. The frequency can be 150-175MHz. This is how the Module looks like.


To the left is the power input pin. Then comes power control, main power line and to the right is the output power. As you see there are quit many components inside and both input and output are matched to 50 ohm.


RF Power Amplifier Module S-AV10H TOSHIBA Schematic
The main part of this project is an oscillator which you will find on the left side. It is an oscillator based around Q1. L1 and C1 forms the tuned oscillating unit. The unit can easy be set from 100 to 200MHz by changing C1 and spacing/compressing the aircoil L1. You can see the air coil at the botoom left corner on the first photo at this page. Q2 works as a booster and amplify the power to 150mW.


The RF signal then enter the Module at pin 1. Pin 2 is a power control unit of the Module. The voltage at this pin will set the output power of the Module. A voltage stabiliser LM317 is added to generate a variable voltage from 1.25V to 12 V. You can see it in the middle of the PCB and in front if it is a 10 turn potentiometer (P1). An inductor blocks RF from the Module to pass out to the power line of the LM317. Pin 3 of the module is the main power input which also is RF blocked by an inductor. Theses inductors are not critical in any was, make sure they can handle high currents since the module will consume high current.
Pin 4 of the module is the power output matched to 50 ohm system.

You must use a dummy resistor of 50 ohm else you will destroy the module. Make sure you choose a good resistor which can handle 30-50W. Make sure you have placed the Module to a heat sink becasue it will be hot.

RF Power Amplifier Measurements
The output power from this module could be set from a few mW to about 18 W by the voltage at Control pin. The unit was stable down to 145MHz and current was about 2.2A at max output power.

Source: RF Power Amplifier Module