125MHz peak detector Help optimize circuit
时间：04-04
整理：3721RD
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Hi, I need a peak detector working at 125MHz to measure a variable capacitance between 4pF to 30pF
The oscillator outputs 0V to 3,3V square wave at 125MHz and I need to get a proportional DC voltage output to capacitance value (4pF to 30pF).
First all, will diode 1N4148 work well at 125MHz? or is there any better suitable diode for this circuit? Diode 1N4148 is showed to work at 100MHz with a rectifier efficiency of 45% (seen on datasheet). Maybe need a UHF diode with faster switching time and lower switching capacitance..
I tested the circuit below at 75MHz and voltage output is around 1,6V with capacitance at 4pF and 1,9V with capacitance at 30pF this means 300mV difference.
The circuit is not optimized but output DC difference is not bad at all.. I also added an ampop to buffer output voltage.
Could anyone help me to improve this circuit to work optimized at 125MHz A simulation would be great.. Is this the best design or is there another better way to measure this variable capacitance?
Any help is welcome Thanks.
The oscillator outputs 0V to 3,3V square wave at 125MHz and I need to get a proportional DC voltage output to capacitance value (4pF to 30pF).
First all, will diode 1N4148 work well at 125MHz? or is there any better suitable diode for this circuit? Diode 1N4148 is showed to work at 100MHz with a rectifier efficiency of 45% (seen on datasheet). Maybe need a UHF diode with faster switching time and lower switching capacitance..
I tested the circuit below at 75MHz and voltage output is around 1,6V with capacitance at 4pF and 1,9V with capacitance at 30pF this means 300mV difference.
The circuit is not optimized but output DC difference is not bad at all.. I also added an ampop to buffer output voltage.
Could anyone help me to improve this circuit to work optimized at 125MHz A simulation would be great.. Is this the best design or is there another better way to measure this variable capacitance?
Any help is welcome Thanks.
