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#1
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IC OpAmp Question
Hi
Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? To be specific, I'm looking at the LT 1028. Thanks for any input Samuel |
#2
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Samuel Groner wrote:
Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? To be specific, I'm looking at the LT 1028. It usually says so in the data sheets. Aside from the "electrical characteristics" you have to look at the "absolute maximum ratings." For example, the LT1028 specifies a maximum power supply voltage of +/-22V, and a maximum input voltage of "Equal to Supply Voltage." Of course in practice you don't want to run 22V rails because if they drift even slightly you'll risk destroying the device. Run 20V rails to be safe, or use 22V regulators followed by a series diode or 10-ohm resistor (with local decoupling caps) to give yourself a little margin. To answer your question, yes. The higher supply voltage buys you greater headroom on the input and the output. ulysses |
#3
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Samuel Groner wrote:
Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? To be specific, I'm looking at the LT 1028. It usually says so in the data sheets. Aside from the "electrical characteristics" you have to look at the "absolute maximum ratings." For example, the LT1028 specifies a maximum power supply voltage of +/-22V, and a maximum input voltage of "Equal to Supply Voltage." Of course in practice you don't want to run 22V rails because if they drift even slightly you'll risk destroying the device. Run 20V rails to be safe, or use 22V regulators followed by a series diode or 10-ohm resistor (with local decoupling caps) to give yourself a little margin. To answer your question, yes. The higher supply voltage buys you greater headroom on the input and the output. ulysses |
#4
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To answer your question, yes. The higher supply voltage buys you
greater headroom on the input and the output. Thanks! Samuel |
#5
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To answer your question, yes. The higher supply voltage buys you
greater headroom on the input and the output. Thanks! Samuel |
#6
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Samuel Groner wrote:
Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? You mean wider output swing? Maybe, it depends on the IC. To be specific, I'm looking at the LT 1028. Look on the data sheet about output swing with different voltages. Since many of the reference voltages inside are regulated, higher supply rails may or may not be a help. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#7
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Samuel Groner wrote:
Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? You mean wider output swing? Maybe, it depends on the IC. To be specific, I'm looking at the LT 1028. Look on the data sheet about output swing with different voltages. Since many of the reference voltages inside are regulated, higher supply rails may or may not be a help. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#8
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In article ,
Justin Ulysses Morse wrote: Samuel Groner wrote: Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? To be specific, I'm looking at the LT 1028. It usually says so in the data sheets. Aside from the "electrical characteristics" you have to look at the "absolute maximum ratings." [snip] All this is correct, but also look at the idling dissipation specs as well. You need to multiply the total power supply current by the voltage drop across the two supply leads to determine the dissipation. This must also be kept below the absolute maximum, and you also have to consider the load current as well. This isn't always an issue, but with some surface mount packages, some op amps and some circuit applications, you might need a heatsink or extra foil on the PC board to dissipate some heat. Regards, Monte McGuire |
#9
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In article ,
Justin Ulysses Morse wrote: Samuel Groner wrote: Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? To be specific, I'm looking at the LT 1028. It usually says so in the data sheets. Aside from the "electrical characteristics" you have to look at the "absolute maximum ratings." [snip] All this is correct, but also look at the idling dissipation specs as well. You need to multiply the total power supply current by the voltage drop across the two supply leads to determine the dissipation. This must also be kept below the absolute maximum, and you also have to consider the load current as well. This isn't always an issue, but with some surface mount packages, some op amps and some circuit applications, you might need a heatsink or extra foil on the PC board to dissipate some heat. Regards, Monte McGuire |
#11
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#13
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"Mike Rivers" wrote in message news:znr1084800008k@trad... In article writes: Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? You might get more smoke. Most 15V op amps will take 18V, but 22 is usually too much. Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. He did look at the spec sheet; the 1028 is spec'd for +/- 22V maximum. I'd run it closer to 21 for safety's sake, but this chip works quite nicely at that voltage. It does run kinda hot, though, even at +/- 15V, and I'd suggest one of those little glue-on heatsinks. Peace, Paul |
#14
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Most 15V op amps will take 18V, but 22 is usually too much.
Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. The LT1028 takes 22V and no, the max. output swing with 22V is not specified (or I just do not see it). Samuel |
#15
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Most 15V op amps will take 18V, but 22 is usually too much.
Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. The LT1028 takes 22V and no, the max. output swing with 22V is not specified (or I just do not see it). Samuel |
#16
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Samuel Groner wrote:
Most 15V op amps will take 18V, but 22 is usually too much. Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. The LT1028 takes 22V and no, the max. output swing with 22V is not specified (or I just do not see it). In the data sheet I have for the LT1028, in the "absolute maximum ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. ulysses |
#17
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Samuel Groner wrote:
Most 15V op amps will take 18V, but 22 is usually too much. Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. The LT1028 takes 22V and no, the max. output swing with 22V is not specified (or I just do not see it). In the data sheet I have for the LT1028, in the "absolute maximum ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. ulysses |
#18
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Paul Stamler wrote:
works quite nicely at that voltage. It does run kinda hot, though, even at +/- 15V, and I'd suggest one of those little glue-on heatsinks. Yeah, but don't use a 'hot-melt' glue gun ! geoff |
#19
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Paul Stamler wrote:
works quite nicely at that voltage. It does run kinda hot, though, even at +/- 15V, and I'd suggest one of those little glue-on heatsinks. Yeah, but don't use a 'hot-melt' glue gun ! geoff |
#20
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Paul Stamler wrote:
"Mike Rivers" wrote in message news:znr1084800008k@trad... In article writes: Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? You might get more smoke. Most 15V op amps will take 18V, but 22 is usually too much. Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. He did look at the spec sheet; the 1028 is spec'd for +/- 22V maximum. I'd run it closer to 21 for safety's sake, but this chip works quite nicely at that voltage. It does run kinda hot, though, even at +/- 15V, and I'd suggest one of those little glue-on heatsinks. The 5532 is rated at +/- 20 volt supply http://focus.ti.com/lit/ds/symlink/ne5532.pdf The 5534 is rated at +/- 22 volt supply http://focus.ti.com/lit/ds/symlink/ne5534.pdf The OPA604 is rated at +/- 24 volt supply http://focus.ti.com/lit/ds/symlink/opa604.pdf |
#21
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Paul Stamler wrote:
"Mike Rivers" wrote in message news:znr1084800008k@trad... In article writes: Most IC opamp data sheets spec max. input and output voltage with PS @ +-15 V; if I use +-22 V, do I gain more volts here? You might get more smoke. Most 15V op amps will take 18V, but 22 is usually too much. Look at the spec sheet for the op amp you have in mind, and don't exceed the maximum ratings. He did look at the spec sheet; the 1028 is spec'd for +/- 22V maximum. I'd run it closer to 21 for safety's sake, but this chip works quite nicely at that voltage. It does run kinda hot, though, even at +/- 15V, and I'd suggest one of those little glue-on heatsinks. The 5532 is rated at +/- 20 volt supply http://focus.ti.com/lit/ds/symlink/ne5532.pdf The 5534 is rated at +/- 22 volt supply http://focus.ti.com/lit/ds/symlink/ne5534.pdf The OPA604 is rated at +/- 24 volt supply http://focus.ti.com/lit/ds/symlink/opa604.pdf |
#22
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In the data sheet I have for the LT1028, in the "absolute maximum
ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. You are not saying that max. out is always equal to max. in, are you? Samuel |
#23
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In the data sheet I have for the LT1028, in the "absolute maximum
ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. You are not saying that max. out is always equal to max. in, are you? Samuel |
#24
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Samuel Groner wrote:
In the data sheet I have for the LT1028, in the "absolute maximum ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. You are not saying that max. out is always equal to max. in, are you? Samuel No, I'm not saying that. I'm saying I didn't read the data sheet closely the first time. But I do suspect that the max out should be within a couple of diode drops of the power supply voltage in most devices. That is to say, higher rails *should* generally give you higher output swing to some extent. ulysses |
#25
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Samuel Groner wrote:
In the data sheet I have for the LT1028, in the "absolute maximum ratings" section it says... Oh, you're right, it gives the max input (which is equal to the rail voltages) and not the max output. You are not saying that max. out is always equal to max. in, are you? Samuel No, I'm not saying that. I'm saying I didn't read the data sheet closely the first time. But I do suspect that the max out should be within a couple of diode drops of the power supply voltage in most devices. That is to say, higher rails *should* generally give you higher output swing to some extent. ulysses |
#26
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#27
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#28
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Thanks for all replies!
Samuel |
#29
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Thanks for all replies!
Samuel |
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