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Old 25th January 2006, 02:38 PM   #1
Bazukaz is offline Bazukaz  Lithuania
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Default Bridging many op amps

Hi,
Is it possible to bridge more than 2 op amps , lets say , 8 ?
I need higher voltage and low current at output. I would use LM833 or similar op amps.


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Lukas.
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Old 25th January 2006, 02:56 PM   #2
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You mean bridge them, then parallel a few to get more current? The bridging bit is OK (what will you be driving though - it needs to be floating). Would be a load easier to just add an output stage or BUF634 though.
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Old 25th January 2006, 03:01 PM   #3
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No , i don't need to paralell them. I need an output voltage of around 200V Rms and very low current. I need it to drive audio signal - now i am thinking about 3584JM chip - is it suitable for audio frequencies ?
I was unable to find it's distortion curves.

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Lukas
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Old 25th January 2006, 03:13 PM   #4
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how about bridge 2 lm7402 they can have +- 75v supply is that enough?

http://www.national.com/pf/LM/LM4702.html

but for low current output you would not use the transistors that they have in the datasheet
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Old 25th January 2006, 03:24 PM   #5
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Quote:
Operation

The maximum power of the amplifier is primarily set by the supply voltage (18V). The maximum output voltage is approximately 16V. With 8 ohm speakers, the power rating is 16 Watts per channel. With 4 ohm speakers, the power rating doubles (32W per channel). Continuous power output equals the peak power output since, except for the supply voltage, power supply is "over-dimensioned".

Each LM6171 opamp is able to deliver up to 150 mA of current, we have 6.6 Amps per channel.

With 16V output, the amp should drive loudspeakers down to 2.5 ohm. In this case, the output impedance effectively seen by each separate opamp is 44 x 2.5 + 10 = 120 ohms and does not represent a major problem (LM6171 is specified for impedances down to 50 ohms).
This amplifier uses 44 op-amps LM6171 in parallel


Click the image to open in full size.

more info A Precision Preamplifier-Power Amplifier System
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Old 25th January 2006, 03:27 PM   #6
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You need to look at output stages with gain. I have just the circuit in a book by Walt Jung somewhere at home, only uses a few components.
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Old 25th January 2006, 03:32 PM   #7
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Quote:
Originally posted by Bazukaz
I need an output voltage of around 200V Rms and very low current. I need it to drive audio signal
200 Vrms needs a power supply of +300Volt, 0 Volt and -300 Volt

I think you should forget Op-Amps

Think high voltage transistors or tubes for this.
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Old 25th January 2006, 04:26 PM   #8
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Step up transformer?
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Old 25th January 2006, 05:43 PM   #9
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I don't want to use output trannie generally , so an ap-amp with high voltage transistor would be OK. It could operate in class A mode , but where to find a schematic ?
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Old 25th January 2006, 06:46 PM   #10
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http://216.253.197.8/mainsite/products/linvoltage.asp

http://216.253.197.8/mainsite/produc..._amps/pa89.asp

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