Slightly OT : Looking for High Voltage OPAMP Supplier

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Hello everybody,

I'm delving in an embedded project that needs among other things to move
some optical elements using some piezo PZT stack actuators . Big deal, I
thought in the beginning . The current drive requirements are low, short
pulses of up to 30mA , with a low duty cycle, and operating voltage of up to
60Vdc , single source .
 When it came the time to implement a solution, Apex came to mind .
Surprise, they only have now all sorts of high power devices ,
astronomically priced, in huge TO-3 or TO-220 packages, running up to
hundreds of volts and delivering up to several Amps in capacitive loads. I
started searching all the good old opamp makers and some specialty high
voltage opamp houses . Burr Brown, swallowed by TI, Elantec, swallowed by
Intersil, Analog DEvices, no high voltage , Maxim, no high voltage , Linear
Tech , no high voltage , Natsemi, no high voltage . Apex , lots of
1000V/10A/$100 devices , in TO-3 packages !
I looked at audio amps as well, in the hope of finding that elusive $2 ,
surface mount plastic package that would run at 60Vdc, which is what I need
. No such luck yet.

I'm asking here, although this is not strictly embedded , maybe someone
knows of a current produciton device with the following specs:
-operating supply voltage up to 60Vdc , or higher , to allow an approximate
output swing of 60V , or split supply of  +/-30V or higher if not rail to
rail output , to allow the same output swing of 60v.
-max output current 30mA pulses shorter than 1ms , repeated with a max duty
cycle of 20% .
-plastic package, SMD .
-low cost, under $4.
-multiple , dual or quads would work even better.

Any pointers would be greatly appreciated.

thank you,
matt tudor

Re: Slightly OT : Looking for High Voltage OPAMP Supplier
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  As you have found, this is a little bit of no-mans-land : you need to
look for a volume usage device that can be used in your niche.

  Look at CRT drivers eg,1850,952,00.html

  These are high voltage, low cost, 3x, and have class AB drive, and
CRT drive is a large market segment, with a range of Speed/Voltage choices.

Re: Slightly OT : Looking for High Voltage OPAMP Supplier
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Try looking at the L6660 MILLI-ACTUATOR DRIVER from ST. It is a resonant
converter that is able to drive +/-35V, or 0-70V at better than 60mA
with a 12V supply. I don't know anything the price or availability...
Otherwise take a look in Art of Electronics 2nd edition for the simple
piezo driver circuit. I have used that circuit and you easily implement
a variation of it that fits within your budget constraints.


Re: Slightly OT : Looking for High Voltage OPAMP Supplier

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Do you need accurate pulse amplitudes i.e. the output must be in the
op-amp feedback loop ?

Do you need both current sinking and sourcing capability ?

If only sinking capability needed, look for those NPN darlington
arrays with 7 or 8 transistors. If feedback is used, the feedback
resistors will drop the feedback voltage well below 30 V, so ordinary
30 V op-amps can be used to drive the darlingtons. The driving op-amp
output must be able to go to the negative supply (ground) in order to
fully cut off the darlingtons. Since there are a 7-8 drivers in each
IC, the chip count should not be a problem if multiple channels are

However, if both sinking and sourcing are needed, you would also have
to use some individual PNP transistors to sink the current, since I am
not aware of any PNP driver chips with multiple  common emitter
drivers. Additionally some resistors are needed, so the chip count can
be quite large when multiple channels are needed.

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The 60 Vdc supply would allow 20 Vrms or 50 or 100 W into 8 resp. 4
ohms, so no wonder that you did not find anything in that price class.
At least previously, a few high voltage driver ICs existed, which
required the addition of two high current, high power transistors to
make a complete 50-200 W audio amplifier.  Look for such driver ICs,
since they should alone be able to drive the 30 mA load.


Re: Slightly OT : Looking for High Voltage OPAMP Supplier

Paul Keinanen wrote in message ...
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I need analog outputs, not PWM or logic. The PZT actuators have nanometer
resolution and over 10 micron displacement range .

The audio driver stage Ic's that you're mentioning have disappeared from
product lines of all major maunfacturers that I am familiar with . 10-20
yearsd ago they were produced by multiple vendors, now they're gone ,
rpelaced by higher scale integration, switching integrated audio amplifiers
, etc.

The CRT video drivers come close but no cigar, because CRT's have low
capacitance , in the tens of pF , whereas the PZT actuators are in the tens
of nanos or larger .

The ST L6660 is the closest to my needs, just have to source it now, and a
search for it on major US distys websites failed .  The ST website shows a
datasheet for it dated 2000 , and marked preliminary . Doesn't smell good .

best regards,
matt tudor

Re: Slightly OT : Looking for High Voltage OPAMP Supplier
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Matt et all,

Assuming you need to reproduce a waveform @high voltage, the
TI/Burr-Brown OPA452 meets the electrical specs, but is (at ~$5 {price
from digikey}) a bit over the target price.  The Harris (now intersil)
HA-2645 will handle the voltage swing, but would need a push-pull pair
to handle the current.  Both are single channel devices.  So, the CRT
drivers may well be the better choice.  If you just need a short
pulse, why not use MOSFET(s) to switch?

A post to may garner more ideas.



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