Supplier!

[epilot]

Hello,

Suppose you have a split (dual) supply with + & - and ground pins.
Well now you design a circuit which has to work with an dual supply(like an Op Amp) then you design another circuit which must work with a single supply source(you use the + and ground of the dual supplier),
You want to connect 2 circuits together, can you make the job without any special matching??

Even suppose you have an dual source Op Amp or amplifier (+&-10V)and want to connect it to a
circuit made of TTL chips and works just with 5V. then do you use the + and ground of you dual supplier for TTL circuit and then connect its output to your Op Amp or amplifier?

Thanks

 

[audioguru]

The output of the opamp that has a +10V and -10V dual supply will go from about +8V to -8V. If you feed +8V or -8V to the input of a TTL IC then it will get broken. Read the max voltage limits on the TTL datasheets.

Use a voltage divider or protection diodes to limit the opamp signal to between 0V and +5V.

 

[Oznog]

first part... can't answer without a specific circuit. Components may be required for "special matching".

can't even understand what you're saying in the second part.

 

[audioguru]

I think maybe all the wars that are going on over there are messing up which circuit is feeding which.

 

[epilot]

The output of the opamp that has a +10V and -10V dual supply will go from about +8V to -8V. If you feed +8V or -8V to the input of a TTL IC then it will get broken. Read the max voltage limits on the TTL datasheets.

Use a voltage divider or protection diodes to limit the opamp signal to between 0V and +5V.

I never said I want to feed the Op Amp output to the TTL input, I want to connect the output of the TTL chip into the input of the Op Amp

 

[audioguru]

TTL output voltages are about 0.4V and 2.6V.
If the opamp's ground is connected to the TTL's ground, the opamp has a dual supply and the opamp circuit has a gain of +1, then its output voltages will be exactly the same as its input voltages: 0.4V and +2.6V.
If the opamp's ground is connected to the TTL's ground, and the opamp circuit has a gain of -1, then its output voltages will be -0.4V and -2.6V.

 

[epilot]

TTL output voltages are about 0.4V and 2.6V.
If the opamp's ground is connected to the TTL's ground, the opamp has a dual supply and the opamp circuit has a gain of +1, then its output voltages will be exactly the same as its input voltages: 0.4V and +2.6V.
If the opamp's ground is connected to the TTL's ground, and the opamp circuit has a gain of -1, then its output voltages will be -0.4V and -2.6V.

But I need a general response for connecting another circuits(with the same problem) together

For example see this filter too.
It looks like the circuit needs a dual supply for the Op Amps while I want to connect its output to a single supply circuit(the positive and ground will be common for 2 circuits), but I don't know how to do the job?
I fear which could not get a perfect response If use dual supply for the filter while the second circuit has a singel supply....

 

[audioguru]

The analog circuit has an idle output voltage of 0V and its output swings positive and negative up to about 13V peak.

1) Why feed an analog signal to a digital circuit?
2) The negative swing of the signal to the input of TTL logic will destroy the TTL.
3) The 13V swing to the input of TTL logic will destroy the TTL.

You need to modify the signal so that it fits into the TTL input voltage range of 0V to +5V. Attenuate it then add an offset voltage.

 

[epilot]

The analog circuit has an idle output voltage of 0V and its output swings positive and negative up to about 13V peak.

1) Why feed an analog signal to a digital circuit?
2) The negative swing of the signal to the input of TTL logic will destroy the TTL.
3) The 13V swing to the input of TTL logic will destroy the TTL.

You need to modify the signal so that it fits into the TTL input voltage range of 0V to +5V. Attenuate it then add an offset voltage.

Why don't use a voltage splitter to create a virtual zero point like this pic?

 

[epilot]

audioguru,
Here is another dual circuit from you for example which I follow an alternative to modify it to a singel ended supply?
Thats why I am saying I need a general response.

 

[audioguru]

Your voltage splitter circuit has too many parts. An opamp just needs a two resistors voltage divider and a filter capacitor to make a virtual ground and work with a single supply.

You have a differential amplifier made from an opamp. Why?

 

[Nigel Goodwin]

audioguru,
Here is another dual circuit from you for example which I follow an alternative to modify it to a singel ended supply?
Thats why I am saying I need a general response.

As Audioguru has already said, all you need is two resistors and a capacitor!.

 

[epilot]

Can you let me have the configuration with 2 resistors for a Differential amplifier?
I know how to do the job for an inverting and non inverting configuration, but I am not sure how to do the job for an differential circuit?

What about the phasing circuit I have shew in the 7 post?

 

[Nigel Goodwin]

Can you let me have the configuration with 2 resistors for a Differential amplifier?
I know how to do the job for an inverting and non inverting configuration, but I am not sure how to do the job for an differential circuit?

The 'ground' connection (bottom of 220K) goes to the centre of the two resistors, it's as simple as that - however, if the inputs and outputs are DC coupled everything else has to be referenced to the same 'virtual' centre point.

What about the phasing circuit I have shew in the 7 post?

Just as above - bear in mind though with a simple two resistor method you have to be careful that the current demands per supply rail are equal to each other!.

 

[epilot]

The 'ground' connection (bottom of 220K) goes to the centre of the two resistors, it's as simple as that - however, if the inputs and outputs are DC coupled everything else has to be referenced to the same 'virtual' centre point.



Just as above - bear in mind though with a simple two resistor method you have to be careful that the current demands per supply rail are equal to each other!.

Thanks Nigel,

But how to calculate 2 resistors value?

You said that I need for a capacitor too.

by the way as the filter is a phaser circuit I fear to use 2 resistors meathod for it.

 

[Nigel Goodwin]

Thanks Nigel,

But how to calculate 2 resistors value?

It's just a potential divider - try 4K7.

You said that I need for a capacitor too.

Just a decoupling capacitor, try 47uF.

by the way as the filter is a phaser circuit I fear to use 2 resistors meathod for it.

Makes no difference, it's simply making a virtual split supply.

 

[Hero999]

It's also normal to bypass each resistor in the potential divider with a 100nF capacitor.