# Changing the frequency

Discussion in 'General Electronics Chat' started by johnny23, Jun 15, 2014.

1. ### johnny23 Thread Starter New Member

Jun 15, 2014
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If you want to make a circuit that receives a triangle wave with a known frequency and changes it while maintaining the amplitude, do you have to transform into DC and then generate a new triangle wave (which is not easy, i guess) or are there easier ways?

2. ### crutschow Expert

Mar 14, 2008
21,757
6,271
Can't think of an easier way. You could use a positive and negative peak detector to set the positive and negative peak values for the new frequency. Is this from one fixed frequency to another fixed frequency or are the frequencies variable?

johnny23 likes this.
3. ### johnny23 Thread Starter New Member

Jun 15, 2014
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Yes. A fixed known frequency will enter the circuit, and I want to multiply that frequency by 4, without changing the amplitude

4. ### crutschow Expert

Mar 14, 2008
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So this fixed frequency will not vary in frequency?

5. ### johnny23 Thread Starter New Member

Jun 15, 2014
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for example, if i know the input is always going to be a triangle wave with 50k Hz and amplitude A, i want to make a circuit in which the output is always a triangle wave with 200k Hz and amplitude A

6. ### crutschow Expert

Mar 14, 2008
21,757
6,271
Does the output frequency need to be exactly 4 times the input frequency?

What's the purpose of this output?

7. ### johnny23 Thread Starter New Member

Jun 15, 2014
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Not exactly, but with something like 90% precision.

8. ### Brownout Well-Known Member

Jan 10, 2012
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This is easy. The triangle already has 4 distinct time points that can be references to product a new frequency. You have the peak max, min and two zero crossings ( use a capacitor if needed ) now you can use these 4 points to generate a signal of twice the frequency. Do this twice, and you have 4x frequency.

9. ### MrChips Moderator

Oct 2, 2009
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What is your application? Is this homework?

Last edited: Jun 15, 2014