- 1 Terms and Definitions
- 2 References
- 3 Introduction
- 4 Background Concept
- 5探测器电路
- 6 Power Amplifier
- 7 Digital Step Attenuator
- 8 Low Noise Amplifier
- 9 SLG46582V GreenPAK Schematic
- 10 IC Circuit Features
- 11 Operation
- 12 Pin Descriptions
- 13 Raspberry Pi Control Software
- 14 Measurements
- 15 Further Design Considerations
15 Further Design Considerations
GreenPAK Comparators: During attenuation testing, it was discovered that the outputs of comparators in the GreenPAK devices do not instantly switch output states (high to low or low to high) upon hitting the threshold voltage. Rather, the output voltage from the comparator begins to drop at threshold and continues dropping linearly as the input voltage continues to drop below the reference voltage. It appears the gain and loop bandwidth of the comparators are not sufficiently high to switch right at threshold or shortly lower. The same holds true as the input voltage begins to increase and rise toward the reference voltage. Using an external Vref with precision resistors to set the voltage may improve this performance. That was not done in this example. Additionally, there are no additional pins available to use external references.
Detector Design: As discussed previously, the design of the detector circuit could be improved in both sensitivity, loss and overall performance. This design was sufficient to show the performance of the circuit.
Test Equipment: The Mini-Circuits portable test equipment pieces are excellent and low cost. However, should precise measurements need to be made including possible spectral degradation at the bias cross-over point, higher performance test equipment would be needed. At this time, it is unknown what performance impact would take place with the RF signal at the transition point between bias settings. This could be explored further in depth and we welcome any feedback on this.
Higher Power RF Amplifiers: If a similar circuit is desired for amplifiers that run with higher bias current than the SLG46582 is able to provide, a similar design has been done utilizing the Dialog SLG46867V GreenPAK IC. This GreenPAK has dual 2 A Power FET switches. The circuit switches between the two power FETs to change the bias point of the amplifier. The user would need to provide their own regulated voltages for each bias state (up to 6 V max). Please contact the author if this circuit is desired.