In Part 1 of this article, we introduced RF design using op amps. In Part 2, we address practical circuit examples of RF and intermediate frequency (IF) amplifiers.
Part 1 of this article introduced the "How's and Why's" of RF design with op amps. However, this information is valueless unless working circuits can be constructed and measurements taken to prove the concept. This part describes wideband RF and narrow band IF amps. Except where noted, this article speaks of voltage gain of the stage.
Wideband RF Amplifiers
As discussed in Part 1 , it is best to use current feedback amplifiers for RF design. We chose to use the THS3202 2 GHz low-distortion, current-feedback amplifiers as an example due to their wide bandwidth and fast slew rate. For example, the circuit of Figure 1 produces an amplifier voltage gain of 20, and a stage voltage gain of 10.
1. Wideband RF Amplifier.
This circuit in Figure 1 produces the amplitude curve illustrated in Figure 2.
2. Wideband Response for Circuit of Figure 1.