Questions tagged [varicap]

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How to adapt a FM reciever circuit to use a varicap diode instead of a trimmer capacitor

My team and I are interested in learning about FM communication and decided to build a simple FM receiver before building a proper transmitter. We looked at some circuits on the web, and they all seem ...
Candy Hi's user avatar
  • 141
0 votes
2 answers
783 views

Can anyone help me in designing this variable frequency colpitt oscillator?

I am basically trying to achieve a variable frequency colpitt oscillator by using a varactor diode to achieve frequency change. However, I am having trouble figuring out how to connect it so that it ...
needbrainscratched's user avatar
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1 answer
340 views

How to define the circuit that replaces the variable capacitor in its use with the TDA7000?

In the circuit below, there is a subcircuit that connects between C4, D1 and the VCC (5V), with Q1 and D2 as the central component, this circuit seems to me to be a Gyrator, I know that Gyrators are a ...
Delfino's user avatar
  • 283
2 votes
2 answers
2k 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 ...
Mr X's user avatar
  • 734
7 votes
2 answers
378 views

1977 GE 6RS20SP9B9 - what the heck is this component?

Ok so, ordinarily I'd not ask a "what is this" question, but this component really has me scratching my head - both at its function in the circuit and how it is constructed. Anyone know what a GE ...
rdtsc's user avatar
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2 votes
3 answers
267 views

Multi-tuning AM selector

I'm thinking about the design of an AM receiver frontend that needs to select between three channels. The community suggested that I investigate manually wound loop antennas, and they seem like a nice ...
Reinderien's user avatar
  • 3,189
2 votes
1 answer
2k views

Simulating varicap diode in LTSpice

I have been looking into making a voltage controlled oscillator using varicap diodes, however I have had hard time simulating the diodes in spice. Would anyone here have an idea how this would be ...
user3120921's user avatar
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0 answers
453 views

How can I create a varicap in ADS?

I need to create a varying capacitor, so I'm trying to make a varicap in ADS. However, there are only diodes, and I don't know how to make a varicap. Can you point me to some resources or walk me ...
JobHunter69's user avatar
1 vote
1 answer
801 views

Is BBY40 a good substitute for MV209 in this RF receiver?

VD1, indicated by the red circle in this is a varactor diode and the suggestion given for the varactor diode in this manual is MV209. It seems to be outdated and so are many other components. How do ...
Mathav Raj's user avatar
1 vote
2 answers
3k views

Using a varactor diode to tune a resonance frequency

I think this is a question is some very elementary circuit design but... I want to use a varactor diode to tune the resonance frequency of a resonator I have built. I understand that a varactor is a ...
user27119's user avatar
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1 vote
1 answer
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VCO doesn't work

I've tried to design a voltage controlled oscillator by adding a varactor to a Colpitts oscillator. However simulation shows no change in the oscillation frequency as V3 changes (0.04v to 10v). I ...
SMA.D's user avatar
  • 505
-1 votes
3 answers
260 views

Can you switch between 2 tank circuits using a relay?

Say I have an oscillator that needs to span between 1 GHz and 1 Mhz. Ill be controlling it with a microcontroller, probably an arduino. According to this, http://faculty.mu.edu.sa/public/uploads/...
user2455722's user avatar
0 votes
2 answers
546 views

How to boost (double voltage) a sawtooth generator

I have a circuit to drive, using a sawtooth generator, four varactor diodes (FC54). These varactor diodes has the following specs: from 2.5pF (at 15V) to 30pF (at 0V), but my sawtooth generator, based ...
Giov's user avatar
  • 41