The PGA-105+ is a 15 dB gain monolithic amplifier for the 40-2600 MHz range with excellent gain flatness and a high dynamic range (1 dB compression point: 19.3 dBm @ 2 GHz).

S-parameters for the PGA-105+ can be found here. Unconditional stability requires stability factor k>1 and stability measure B>0. However, an analysis of the S-parameters shows the amplifier has k<1 for frequencies under 60 MHz.

Figure 1: PGA-105+: Stability parameters.

In order to improve stability, addition components need to be added at input and output, see Figure 2:

Figure 2: Stabilization circuit.
Figure 2: Stabilization circuit.

The stability parameters of the amplifier with the stabilizing network are shown in Figure 3. Note: k>1 and B>0 over entire range.

Figure 3: PGA-105+: k-factor.
Figure 4: PGA-105+: k-factor.

The stabilized amplifier has an amplification of about 14.5 dB

The performance of the stabilized amplifier:

Figure 5: Return loss.
Figure 6: Amplification.
Figure 7: Compression.
Figure 8: IP3.
Figure 9: Noise figure.

Conclusion

  • Use of the stabilization circuitry has minor impacts on all parameters.
  • The use of the stabilization circuitry guarantees amplifier’s unconditional stability.

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