buffering a 0V to 36V-DC using an OP-AMP with +/-15V Supply

[payeah]

Hi,

Can anyone show me methods/articles on buffering a 0V to 36V-DC using an OP-AMP with Only +/-15V Supply. how can i reduce the 36V to fit to the +/-15V supply of the op-amp??what op amp configuration should i use?..or can i use a voltage divider to make this possible?...thanks

 

[ericgibbs]

hi,
You would need a >36Vdc source to supply the extra current a buffered 36Vdc output would require.

One way would be a step up SMPS from say +15Vdc to 40Vdc

EDIT:
Do you follow OK.?

 

[payeah]

I dont get it...what is SMPS?...I have an IC that outputs a 36V and I want to buffer it with an op-amp with a supply of +/-15V. How can I reduce the 36V so that it will fit to the buffer op-amp with only +/-15V supply?..refer belowView attachment 67059

 

[ericgibbs]

I dont get it...what is SMPS?...I have an IC that outputs a 36V and I want to buffer it with an op-amp with a supply of +/-15V. How can I reduce the 36V so that it will fit to the buffer op-amp with only +/-15V supply?..refer belowView attachment 67059

hi,
Its not a buffer you need, its a voltage divider.

If you used a divider of say 47K and 10K in series from the +36V and 0V, then the junction of the two resistor would be 6.3Volts, this would be suitable for an OPA of +/-15V supplies.

Connect the 6.3V to the NON inverting input of the OPA.

Is this what you mean?

If you explained what you are trying to do, it would be easier to help you.

 

[payeah]

I need to characterize the performance of the internal charge pump of my IC, charge pump output (CPO) is bonded out on one of DUT's 16 pins. The charge pump block, in nature, is sensitive to its output loading. This loading usually happens externally i.e. voltage meter loading. In order to avoid this external loading, buffer must be inserted between CPO and the meter in the purpose of isolation as well as helps speed up the measurement time. However, most of the amplifers operates in less than 36V in positive rail. To solve the problem I am thinking to put a voltage divider in the input of my buffer op-amp..but what configuration of the op-amp should i use?..inverting?..non-inverting?..can you suggest several configurations?...How about attenuation method??...thanks for your inputs..View attachment 67074

 

[ericgibbs]

hi,
If you require a direct buffered connection to the CPO, it is as I stated in my first post.

In order to create a buffered output from the CPO, the buffer must have a low output impedance and be capable of driving a load that requires more current than the CPO itself can provide.

This means the buffering OPA must be powered with a voltage higher than the 36Vdc output from the CPO. This higher voltage power supply will be source of the higher current flowing into the low output impedance load.

An alternative would be to use a high resistance voltage divider connected from the CPO's 36Vdc output and 0V. Choose resistance values that will not load the CPO output to heavily.

For example, let the divider be 1Megohm and a 100K [ approx 10:1 reduction] say 3.6Vdc

Use a very high input impedance OPA and connect the junction of the resistors to the Non Inverting input of the OPA, the OPA would be configured as non inverting buffer, gain = 1.

Do you follow OK.??

 

[KeepItSimpleStupid]

If you really really want to minimize loading, you can look at high voltage amplifiers. They are not cheap. This https://www.electro-tech-online.com/custompdfs/2012/09/PA81J-82JU_L.pdf is a company that generally specialized in high voltage or high power OP amps. That OP amps boasts 5-50 pA and 10 pf for the input and a unity gain BW of 5 MHz. It does need a +-32 V minimum supply. The part will set you back $161 USD. The Input Z is 10E11 ohms. This may not be the BEST choice.

But it should solve your loading issues. Then put the voltage divider on the output with proper protections.

You did fail to mention the bandwidth and what do you consider loading? 1 G Ohm. 10 M ohms, 100K, 10 K, 1K etc?

As Eric stated, a voltage divider will may work, but you have to define what loading is?

Noton or Transconductance OP Amps can also possibly be used. Their input voltage can generally exceed the supply. Not a type of OP amp that I have played with. See: https://www.electro-tech-online.com/custompdfs/2012/09/MT-034.pdf But the input Z is quite a bit lower like 100K.