Op-amp/ frequency scale question

Status
Not open for further replies.
J

Jason_TTU

New Member
Hello, im trying to scale up a frequency in the 40-80hz range up to a range higher then 5Mhz. Taking a shot in the dark I think I need to use a op-amp with an high gain. I have a MC3403P op-amp that has a 9 MHz Bandwidth. The data sheet can be found here. https://www.fairchildsemi.com/ds/MC/MC3403.pdf
My question is how I can use this op-amp to increase the frequency above 5 MHz or what is a simple way to increase a frequency.
 
It's nothing an opamp could do, but you really need to explain EXACTLY what yo're trying to do - generally if something sounds as silly as this, it's because the original premise is completely wrong.
 

Are talking about generating 5MHz ? Or amplifying at 5MHz? Or something else? Your MC3403 will have very little gain left @ 5MHz.
 
It sounds like what you are trying to build is a mixer:
https://en.wikipedia.org/wiki/Frequency_mixer
Op-amps amplify voltages/currents, you can't "amplify" a frequency - mixers use non-linearity to achieve multiplication to shift a signal in frequency.

As nigel said, you should post a lot more info about exactly what you're trying to do. Given your original post, I think implementing a system with a mixer might be a bit challenging.
 
Look at the datasheet.
The MC3403 has full output up to only 9kHz, not 9MHz. Its gain at 1MHz is only 1 and is less at higher frequencies, but its output cannot swing at high frequencies.

It is a low-power version of a lousy old 741 opamp, but it doesn't have the crossover distortion of a lousy old LM324.
 
Thank you guys for your help. What im trying to do is build a light intensity to frequency converter. I used a voltage to frequency converter. The chip number is k4331 and the data sheet can be found here. https://www.electro-tech-online.com/custompdfs/2007/04/KA331.pdf
I built the circuit shown in figure 3 of the data sheet. This circuit works great and gives me a pulse train out with frequency proportional to the light intensity. My output is between 40 and 80Hz depending on the amount of light I let hit the phototransistor. What I want to do is increase this output somehow to be in the 5+ Mega Hz range
 

I didnt look. The OP said it was 9MHz.. the OP isnt even posting clear questions. I doubt he'll post back anyways..
 
Rather than trying to convert one frequency to another you might be better off thinking about a VCO. That a voltage controlled oscillator. There are lots of circuits available for that frequency and several different ways of deriving the control voltage.

If I have a choice between trusting a distributor and trusting the manufacturer on a published specification I'll pick the manufacturer every time. You did have a link to the actual datasheet. Next time you'll know that high frequency opamps are not bloody likely.
 
Last edited:

Like I said before, tell us EXACTLY what you want to do, and WHY, you're still making no sense, and not giving enough information even if it did make sense.
 
Why in the world do you need it to be in the 5MHz range?

For starters, what I suggested earlier (a mixer) is probably not going to be useful since you clarified that you are talking about a digital pulse train... In case it wasn't made obvious enough already, you REALLY need to be more clear...
 
PLL?

Convert it into a squarewave and then filter the harminics?

A single side band modulator?

All of the above will work but the one you want to use will depend on what you're doing.
 
Status
Not open for further replies.

Similar threads

K
  • Question
Low loss power OR-ing with MOSFETs & Op Amps
Replies
6
Views
1K
Karklebapper
K
J
  • Question
Variable frequency 555 circuit
2
Replies
29
Views
2K
Papabravo
S
  • Question
OP AMP Questions
Replies
16
Views
3K
rjenkinsgb
N
  • Question
Optocoupler Output Question
Replies
2
Views
993
Diver300
D
C
  • Question
An opamp question I can't make sense of
2
Replies
22
Views
2K
MrAl
M
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…