I want to amplify a weak pulse train lets say from 0-0.2V to 0-5V pulses. The reason I'm asking this question; when amplifying I also want to sharpen the rising falling edges of the pulses. Original pulses to be amplified should be sharpened in case of bad shape.
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\$\begingroup\$ Use a comparator, not an opamp. There are different things. http://lmgtfy.com/?q=opamp+comparator+difference \$\endgroup\$– hkBattousaiCommented Mar 25, 2015 at 9:54
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2 Answers
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Use a comparator and if you want really fast edges try the MAX999. It's output voltage will not quite be 5V peak-to-peak but more like 4V peak-to-peak but it's quite suitable for driving a logic input.
The MAX999 has 2.3ns rise and fall times.
Should you require a precise 5Vp-p output I'd still recommend a comparator.
It should be noted that amplifying a signal by (say) 10 does not "sharpen the rising falling edges of the pulses" by 10. If the rise time of the original pulse was 1ms then after amplification the rise time will still be 1ms. If you want to sharpen edges then use a comparator - if you want to preserve amplitude information don't use a comparator - you can't have both.
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\$\begingroup\$ is MAX999 able to adjust amplification as well? is this a Schmitt Trigger? \$\endgroup\$ Commented Mar 25, 2015 at 9:28
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\$\begingroup\$ It's a comparator - when the input level rises above a threshold the output switches. You can't simultaneously amplify AND sharpen edges because that's not what an amplifier does - an amplifier produces a bigger signal but the rise time and fall time of the edges remains the same. \$\endgroup\$– Andy akaCommented Mar 25, 2015 at 9:32
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\$\begingroup\$ the pulse will be between 10Hz to 1000Hz maximum. I want to make a simple circuit by using a comparator and couple of resistors. By this the simple circuit should sharpen the pulses and by the resitors I might be able to adjust the pulse amplitude. Is that possible? Would be great if you draw it if possible? \$\endgroup\$ Commented Mar 25, 2015 at 13:29
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\$\begingroup\$ You can't have a circuit that sharpens pulses and has a linear gain. End of story on that idea. \$\endgroup\$– Andy akaCommented Mar 25, 2015 at 13:30
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\$\begingroup\$ ok i see. so first I should use an opamp and then a schmitt trigger right? which one is first take the input? for a pulse train ranging from 10Hz to 1000Hz any opamp is ok? thnx \$\endgroup\$ Commented Mar 25, 2015 at 13:44
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How fast is your input signal? What is the range of voltage that you expect to see from the signal source?
The reason I ask is that you may be better off with a comparitor configured as a Schmitt trigger rather than an amplifier.
A straight comparitor NOT configured as a Schmitt Trigger might work well for you but the advantage of the Schmitt trigger configuration is that you avoid any ambiguity near the comparitor threshold.
answered Mar 25, 2015 at 9:37
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\$\begingroup\$ the pulse will be between 10Hz to 1000Hz maximum. I want to make a simple circuit by using a comparator and couple of resistors. By this the simple circuit should sharpen the pulses and by the resitors I might be able to adjust the pulse amplitude. Is that possible? Would be great if you draw it if possible? \$\endgroup\$ Commented Mar 25, 2015 at 13:29