Radio Frequency Amplifiers are another workhorse of our Quantumopticians. On one hand, signals are very low and need to be amplified to "see" something, on the other hand, a lot of (lossy) coaxial cable is installed across the laboratory. It is another building block, fully characterised, to be taken from the shelf. We also stock a lot of Mini Circuits Amplifiers, but they often break, because our studens solder 2.5 mm² cables to that poor little feedthru capacitor :-(

The design is straightforward. We use Mini Circuits components for high reliability and high performance. In this case, two times a GVA-81+ (103 mA, 10.5 dB, 19 dBm, 5.0 V), biased by a TCBT-14 (wideband, 10 MHz to 10 GHz, max. 200 mA). The power supply is also onboard. We use a simple linear regulator (LM317), as it allows optimising the supply voltage for a specific Noise Factor / Gain.

S11 : Input Matching

The overall Input Matching is better than 10 dB.

S21 : Gain

The Gain is 20 dB up to approx. 1.0 GHz. Above it decreases slightly, but the device is still useful. This is of course mainly caused by the SCLF-1000+ Lowpassfilter.


S21 : Gain at the lower cut-off

It can be seen clearly, that the specification of the Bias-Tee by Mini Circuits is tentative conservative. Even with two of them, we reach a lower cut-off frequency of better 5 MHz.

S12 : Isolation

The overall Isolation is at least 40 dB.

S22 : Output Matching

The output matching is at least 15 dB, comparable to the input matching.

Blue : Output Power vs. Input Power [dBm], Orange : Gain[dB]
Horizontal : Input Power [dBm]

The maximum Output Power @ 500 MHz is + 19.7 dBm. The Voltage Regulator inside the Amplifier was adjusted to 4.99 V. At 50 MHz the maximum Output Power is + 19.3 dBm, at 1000 MHz + 19.2 dBm.

A view inside the prototype ...

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