Driving LED's from the 12 volt supply will take little current, hence the 2N7000 recommendation.
The OPA2134 will work OK as a straight swap and is even specified down to 5 volt operation.
As the circuit is only driving a visual display, using good quality opamps is a waste. Even the 741 would be fine here (given an appropriate supply)
The OPA2134 will work OK as a straight swap and is even specified down to 5 volt operation.
As the circuit is only driving a visual display, using good quality opamps is a waste. Even the 741 would be fine here (given an appropriate supply)
2N7000 have small max drain current, 280mA continuous and 1500mA pulsed. 3W LED have typical current 700mA and 800mA(peak).
Yes, OPA2134 is over for the application, sure its not a hi-fi circuit. But it would be helpful to know how to correctly compute all values for the particular pre-amp circuit, as it can be useful for another applications.
Yes, OPA2134 is over for the application, sure its not a hi-fi circuit. But it would be helpful to know how to correctly compute all values for the particular pre-amp circuit, as it can be useful for another applications.
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Fair enough, I was thinking of little LED's rather than the big 'uns
Swapping the opamp doesn't affect any of the calculations for gain/response/DC conditions and so on. The OPA2134 will be a direct swap in this application, with the circuit retaining the same specification as if the LM324 had been used.
How to calculate gain, input impedance and so on for opamp circuits can be found in any textbook on the subject.
Swapping the opamp doesn't affect any of the calculations for gain/response/DC conditions and so on. The OPA2134 will be a direct swap in this application, with the circuit retaining the same specification as if the LM324 had been used.
How to calculate gain, input impedance and so on for opamp circuits can be found in any textbook on the subject.
I try design OPA2134 microphone and line-in preamps with WEBENCH Designer online:
OPA2134 | Precision Op Amps | Operational Amplifiers (Op Amps) | Description & parametrics
Should it be inverting or non-inverting type? Also, what should be Desired Input and Output voltage: Vin min / Vin max, Vout min / Vout max, for Mic and Line-in preamps?
OPA2134 | Precision Op Amps | Operational Amplifiers (Op Amps) | Description & parametrics
Should it be inverting or non-inverting type? Also, what should be Desired Input and Output voltage: Vin min / Vin max, Vout min / Vout max, for Mic and Line-in preamps?
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For this colour organ it absolutely doesn't matter what type of design you use.
For audio the design specification depends entirely on your requirements. Line in these days need to accept at least 3 to 4 volts RMS to cope with modern high output digital sources.
So given that most power amps produce full output for 1 volt RMS or less then you really need to ask whether you even need 'gain' at all.
If you are working with older source components such as cassette decks and old tuners then you need to be aiming to see only a couple of hundred millivolts as an output voltage... so those may well need gain.
Mic inputs need gain from a circuit such as this:
http://www.ti.com/lit/ug/tidu765/tidu765.pdf
We are not normally sensitive to absolute phase and so inverting is fine if that gives the other desired specifications you need.
For audio the design specification depends entirely on your requirements. Line in these days need to accept at least 3 to 4 volts RMS to cope with modern high output digital sources.
So given that most power amps produce full output for 1 volt RMS or less then you really need to ask whether you even need 'gain' at all.
If you are working with older source components such as cassette decks and old tuners then you need to be aiming to see only a couple of hundred millivolts as an output voltage... so those may well need gain.
Mic inputs need gain from a circuit such as this:
http://www.ti.com/lit/ug/tidu765/tidu765.pdf
We are not normally sensitive to absolute phase and so inverting is fine if that gives the other desired specifications you need.
So in this case what should be right design criteria inputs for feeding LM324?
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I'm not sure quite what you are trying to do there.
For that configuration (inverting) the reference voltage needs to be Vcc/2. You can alter that for certain situations but audio usually requires symmetrical clipping to maximise the available non distorted output level.
Your numbers don't make sense
Vin max = 5v and Vin min =-5v means you need a gain of 1 or less to get an undistorted output from the opamp on a 12 volt supply.
That lower gain is what is represented by the -0.35 V/V figure.
For that configuration (inverting) the reference voltage needs to be Vcc/2. You can alter that for certain situations but audio usually requires symmetrical clipping to maximise the available non distorted output level.
Your numbers don't make sense
Vin max = 5v and Vin min =-5v means you need a gain of 1 or less to get an undistorted output from the opamp on a 12 volt supply. That lower gain is what is represented by the -0.35 V/V figure.
I'm still not understanding the latest question
To design an opamp preamp stage we need to know as a starting point:
1/ The supply voltage.
2/ The expected input voltage range. A CD player could be as high as 2.4 volts RMS (that's 7 volts pk-pk) at max output (some players are specified above the 2 volt RMS accepted standard).
3/ Your desired input impedance.
To design an opamp preamp stage we need to know as a starting point:
1/ The supply voltage.
2/ The expected input voltage range. A CD player could be as high as 2.4 volts RMS (that's 7 volts pk-pk) at max output (some players are specified above the 2 volt RMS accepted standard).
3/ Your desired input impedance.
The supply voltage puts an absolute limit on how muh voltage you can get from the opamp output. A 12 volt supply means you are looking at around 10 volts of signal as a maximum for a common opamp.
'Common mode' means in a circuit where the two inputs see essentially the same voltage, then that voltage has to stay within given limits... and that often the supply voltage for the opamp as a general rule or as here, the negative supply plus 2.5 volts and the positive supply minus 2.5 volts. So on a -/+15 volts supply you can not drive both inputs to greater than -/+ 12.5 volts.
The input impedance is how much of a load the circuit places on the equipment driving it. Normally we like the input impedance to be high, say over 100k ohms so that it doesn't affect the previous stage. The input impedance of the opamp itself is very very high so high in fact that it doesn't really figure in the equation, it is the components we place around the opamp that determine the final input impedance.
Given that a CD player (any CD player) is going to produce around 2 volts RMS for the very loudest bits on a disc then your preamp running on 12 volts can not have much gain or else it will clip and distort.
'Common mode' means in a circuit where the two inputs see essentially the same voltage, then that voltage has to stay within given limits... and that often the supply voltage for the opamp as a general rule or as here, the negative supply plus 2.5 volts and the positive supply minus 2.5 volts. So on a -/+15 volts supply you can not drive both inputs to greater than -/+ 12.5 volts.
The input impedance is how much of a load the circuit places on the equipment driving it. Normally we like the input impedance to be high, say over 100k ohms so that it doesn't affect the previous stage. The input impedance of the opamp itself is very very high so high in fact that it doesn't really figure in the equation, it is the components we place around the opamp that determine the final input impedance.
Given that a CD player (any CD player) is going to produce around 2 volts RMS for the very loudest bits on a disc then your preamp running on 12 volts can not have much gain or else it will clip and distort.
Those values give you a Vout max of around 10 or 11 volts DC and a minimum of around 1 to 2 volts DC. The output from the opamp would be AC coupled as well as the input.
So the maximum allowable gain would be around 5.3 for that input voltage.
This shows the input voltage (0.1 to 2 volts), the opamp output voltage and the preamp output voltage after AC coupling. Notice how the opamp goes from 1 to 11 volts and also how the output cap makes the final voltage symmetrical around ground.
So the maximum allowable gain would be around 5.3 for that input voltage.
This shows the input voltage (0.1 to 2 volts), the opamp output voltage and the preamp output voltage after AC coupling. Notice how the opamp goes from 1 to 11 volts and also how the output cap makes the final voltage symmetrical around ground.
Attachments
If input signal Vin max amplitude will exceed 2V signal will be clipped?
Looking at this again, yes, since most of modern digital sources produce output more than 1V RMS, which is already sufficient to drive audio Op Amp (LM324), then it doesn’t need another preamplifier. So preamp only needed for microphone input in this case. And Line in input can be directly connected to VR1 trimpot via decoupling capacitor after Mic/Line switch?
Maybe preamp stage can be used just as buffer amplifier to match electrical impedance between the line-in source and LM324 op amp load? Does it make sense?
Looking at this again, yes, since most of modern digital sources produce output more than 1V RMS, which is already sufficient to drive audio Op Amp (LM324), then it doesn’t need another preamplifier. So preamp only needed for microphone input in this case. And Line in input can be directly connected to VR1 trimpot via decoupling capacitor after Mic/Line switch?
Maybe preamp stage can be used just as buffer amplifier to match electrical impedance between the line-in source and LM324 op amp load? Does it make sense?
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You can work it out very simply like this...
For a single rail amp you take the supply voltage and divide it by 2. Now take that result and divide it by root 2. So for example with a 24 volt supply we get (24/2)/√2 which is 8.4
8.4 is the maximum RMS output voltage we can get from a single rail amp running on 24 volts.
When designing the amplifier stage, the maximum RMS input voltage multiplied by the gain of the stage has to give a number less than 8.4, otherwise it clips.
For a single rail amp you take the supply voltage and divide it by 2. Now take that result and divide it by root 2. So for example with a 24 volt supply we get (24/2)/√2 which is 8.4
8.4 is the maximum RMS output voltage we can get from a single rail amp running on 24 volts.
When designing the amplifier stage, the maximum RMS input voltage multiplied by the gain of the stage has to give a number less than 8.4, otherwise it clips.
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