LNA - mixer driver

A low-noise mixer driver converts the voltage of 300 Ω balanced floating source into a current for a mixer.

The signal source is isolated from the ground. It has a differential impedance of 300 Ω and a common-mode impedance of 0.5pF. The frequency range of interest ranges from 1 MHz to 250 MHz.

The load consists of a balanced mixer. It can be represented with two resistors of approximataly 50 Ω, connected to a common-mode power supply of 0.9 V. It should be driven with a differential current with a peak value of 500µA. Common-mode DC current through the load up to 10 mA is allowed.

The low-noise amplifier should have the following properties:

1. Input impedance: 300 Ω ± 5%

2. Frequency range (−3 dB): 1 MHz to 250 MHz

3. Noise figure at 300Ω source impedance: < 2.5 dB over the frequency range of interest.

4. Gain from input voltage to load current 40 mS ± 10%

5. IM3 distortion (test signal: 5 mVp at 200 MHz and 5 mVp at 250 MHz) < −66dB

6. Peak differential output current > 500 µA

7. Supply current at 1.8V supply voltage < 20 mA