# Ultra low power voltage follower

I'm working on a biomedical project, and need to transfer power from a non-ideal source, with a very high internal impedance (~700Kohm) and low voltage, to a load with a high impedance (~1Mohm). I need to maximize the voltage delivered to the load, and because the source has a high internal impedance, I need to have a buffer between the source and the load. Would an op-amp based voltage follower do the job (non-inverting with gain = 1)?

Also, because of the design limitations, I'm trying to find the right op-amp. The priorities are: 1- It must have a low power consumption, 2- It must have a high input impedance, 3- It has to have a low vcc.

I found this from TI http://www.ti.com/product/lpv821 , which seems to satisfy my constraints.

To summarize, my questions are:

1- Is a voltage follower the right circuit? 2- Is the above op-amp suitable for this purpose? Thanks!

Update:

The input source is a low frequency AC signal (less than 1khz) and no DC. The peak to peak input voltage is less than 2.5V and I'm hoping to transfer the same to the load.

The maximum voltage to power the op amp would be 5V (2.5V for positive supply and -2.5 for negative) but the input wont be more than 1.25 in anplitude.

The circuit is meant to work in room temperature.

• define all inputs Vdc , ac and output V for maximum power transfer you must match impedances To Buffer, you must have lower impedance DC – Sunnyskyguy EE75 Mar 14 '18 at 8:08
• Not possible Direct connection would reduce amplitude to 10/17*Vin and with no DC you cant buffer. To create DC would load the signal even more – Sunnyskyguy EE75 Mar 14 '18 at 8:15
• what are you trying to do? Are you trying to get all the power from your 'non-ideal source', or do you have a separate power supply available? – Neil_UK Mar 14 '18 at 8:30
• Ideally, all the power would come from the 'non-ideal source', but I found no way to achieve this without using some active circuit such as op-amp or mosfet which need a separate power supply, but the active circuit has to be very low power. – vmontazeri Mar 14 '18 at 8:37
• Look at the noise PSD, figure 26 in the DS, if you don't need DC you may not want a chopper amplifier. – sstobbe Mar 14 '18 at 16:23