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Questions tagged [varactor]

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99 views

Trouble with FSK VCO modulation circuit

Circuit shown is a VCO that reliably creates a 200MHz sine wave at 3V pk-pk. I would like to use this VCO to create an FSK modulated signal. My bit 1 frequency = 200Mhz and my bit 0 frequency = 205Mhz ...
2
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3answers
94 views

VCO circuit Analysis

can you help me with the basic comprehension of this Voltage Controlled Oscillator scheme (it was used in a PLL)? I do not understand why there are two varactors instead of one, and the role of the ...
1
vote
2answers
210 views

Can Zener or Schottky diodes be used as a substitute for varicap diodes in tuning a VCO?

In particular, this would be a fairly low frequency VCO with a frequency range of 10 Hz to 20 kHz. I'm thinking of the configuration with the T-junction that has 2 opposite facing, reversed biased ...
2
votes
1answer
135 views

How to choose RF choke in the biasing circuit of varactor-tuned resonant circuit

I am new to circuit and has a very basic question about how to set biasing circuit of varactor. I need to use varactor to tune the resonance behavior of Split ring resonator (SRR) structure when ...
0
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2answers
336 views

Direct FM generation using varactor diode

I am trying to generate a constant 1 MHz FM carrier wave. I have achieved it via LC parallel resonance circuit. Initially I let the switch B open and switch A closed, in order to charge the capacitor. ...
0
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2answers
588 views

Changing frequency of 555 timer with varicap or capacitor

I have created a 555 oscillator circuit where the output is set to have flashing LED light. Now I have a problem when I change the voltage of the potentiometer, the output frequency does not change. ...
0
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2answers
43 views

Capacitive voltage divider with varactor

Is it possible to create a capacitive voltage divider where one of the capacitors is a varactor whose capacitance can be manipulated/varied according to a signal? A varactor is a two port device; what ...
2
votes
2answers
73 views

Why are varactors unspecified at 0V?

Specsheets I'm reading tend to specify maximum capacitance at 1V instead of 0V reverse voltage bias. NXP BB series don't show anything below 1V in the tables and 0.5V in the graph. Skyworks SMV ...