H
Hans Wolfenstein
- Jan 1, 1970
- 0
Hello,
I am electronic technician employed at mass spectrometry laboratory.
Current problematics which I am involved includes building a high
voltage, high frequency discrete operational amplifier which can
amplify AC sweeps from 100 kHz to 6 MHz with output voltage swing from
-150 to +150V. Gain is not needed to be more than X10 (we've already
build separate preamp). My idea was using the MOSFETs in the output as
for the differential input I considered the "super match" wide band
dual FETs. Signal is always sine wave which makes job a lot easier.
Load on the output has practically infinite ohmic resistance; only load
is capacitance of measuring cell (which works in high vacuum) of
tipically 30pF (it is a system of metal plates that performs cyclotron
moving of ions but has negligable interaction with ions, much like
deflection electrodes in classic oscilloscope tube, so current should
be very small).
Basic topology of the circuit is standard, includes differential input
(non-inverting and inverting inputs) stage and complementary output
powered with symmetrical PSU.
Before I got employed in this lab my colleagues have made an amplifier
based on APEX opamp but it had significant roll-of at frequencies over
1,5Mhz (despite to nice looking computer simulations), not to mention
the price of these opamps.
Demands are looking "heavy" - there is a large AC voltage swing and wide
freq. bandwidth. Does anybod have recommendation about construction and
parts choice ?
Thank you.
Hans
I am electronic technician employed at mass spectrometry laboratory.
Current problematics which I am involved includes building a high
voltage, high frequency discrete operational amplifier which can
amplify AC sweeps from 100 kHz to 6 MHz with output voltage swing from
-150 to +150V. Gain is not needed to be more than X10 (we've already
build separate preamp). My idea was using the MOSFETs in the output as
for the differential input I considered the "super match" wide band
dual FETs. Signal is always sine wave which makes job a lot easier.
Load on the output has practically infinite ohmic resistance; only load
is capacitance of measuring cell (which works in high vacuum) of
tipically 30pF (it is a system of metal plates that performs cyclotron
moving of ions but has negligable interaction with ions, much like
deflection electrodes in classic oscilloscope tube, so current should
be very small).
Basic topology of the circuit is standard, includes differential input
(non-inverting and inverting inputs) stage and complementary output
powered with symmetrical PSU.
Before I got employed in this lab my colleagues have made an amplifier
based on APEX opamp but it had significant roll-of at frequencies over
1,5Mhz (despite to nice looking computer simulations), not to mention
the price of these opamps.
Demands are looking "heavy" - there is a large AC voltage swing and wide
freq. bandwidth. Does anybod have recommendation about construction and
parts choice ?
Thank you.
Hans