Techniques for Extending the Usable Power Supply Range of the OPA462 High-Voltage Op Amp

Thread Starter

hoyyoth

Joined Mar 21, 2020
308
Dear team,

I was reading this application note and I understood how the circuit works.
Below circuit is taken from the same application note.
But my question is how do we calculate or decide the value of V+ and V- as shown below.



I also read this design note "Design Guide: TIDA-060033 Bootstrap High-Output Voltage-Extension Reference Design ".
This application note also explains the same.

In all these application note V+ and V- is taken as granted. No design for V+ and V- .

May I know how to select value of V+ and V- .Is there any thumb rule exists.

Regards
 

dl324

Joined Mar 30, 2015
16,943
But may I know how do we design VCC and VEE
You use whatever you need and select appropriate transistors and resistor values.

The diodes in series with the resistors compensate for the BE junction drops of the transistors and make it easier to calculate resistor values. The drops across R1 and R3 determine the maximum supply voltage the opamp will see. You want the total resistance to be high enough that they don't take too much of the current the opamp can supply.

I didn't read the article for the circuit you posted, but the one I posted has some limitations. You need to worry about power supply sequencing so you don't experience latch-up. You also need to make sure you operate the opamp inputs within their range, especially if the opamp experiences phase inversion when the input voltage range is exceeded.

EDIT: Note that the Vco and Veo supplies can't be decoupled to ground. Instead, decoupling is across the two supplies (at the bases of the bootstrap transistors).
 
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