Post History
The sensed current may be at a +90V potential (VIN). The LTC2063 op-amp power supply range goes only to +5.25V . It's not a high voltage op-amp. So, the op-amp in this circuit floats just below ...
#2: Post edited
by
Nick Alexeev
·
2025-06-16T14:06:06Z (1 day ago)
The sensed current may be at a +90V potential (V<sub>IN</sub>). The LTC2063 op-amp power supply range goes only to +5.25V . It's not a high voltage op-amp. So, the op-amp in this circuit floats just below the high voltage. That presents two questions.- How to level-shift the output of the current sensor op-amp and reference it to ground?
- M1 and R<sub>DRIVE</sub> act as a level shifter. M1 is tared for more than 90V between drain and source.
- How to create the negative supply voltage for the op-amp?
REF, M2, R2 create a high voltage regulator. It's regulated voltage is referenced to V<sub>IN</sub>, so it's a negative output regulator. The app note says that the negative supply of the op-amp in this circuit is V<sub>IN</sub> - 3V .
- The sensed current may be at a +90V potential (V<sub>IN</sub>). The LTC2063 op-amp power supply range goes only to +5.25V . It's not a high voltage op-amp. So, the op-amp in this circuit floats just below the high voltage rail. That presents two questions.
- How to level-shift the output of the current sensor op-amp and reference it to ground?
- M1 and R<sub>DRIVE</sub> act as a level shifter. M1 is tared for more than 90V between drain and source.
- How to create the negative supply voltage for the op-amp?
- REF, M2, R2 form a linear regulator that's powered from the high voltage rain. It's regulated output voltage is referenced to V<sub>IN</sub>, so it's a negative output regulator. The app note says that the negative supply of the op-amp in this circuit is V<sub>IN</sub> - 3V .
#1: Initial revision
by
Nick Alexeev
·
2025-06-16T00:52:24Z (2 days ago)
The sensed current may be at a +90V potential (V<sub>IN</sub>). The LTC2063 op-amp power supply range goes only to +5.25V . It's not a high voltage op-amp. So, the op-amp in this circuit floats just below the high voltage. That presents two questions. How to level-shift the output of the current sensor op-amp and reference it to ground? M1 and R<sub>DRIVE</sub> act as a level shifter. M1 is tared for more than 90V between drain and source. How to create the negative supply voltage for the op-amp? REF, M2, R2 create a high voltage regulator. It's regulated voltage is referenced to V<sub>IN</sub>, so it's a negative output regulator. The app note says that the negative supply of the op-amp in this circuit is V<sub>IN</sub> - 3V .