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"Ground sensing"? I think what you mean is that the input common mode rangeSomething I want to build with an OP-amp needs the "ground sensing" inputs
like the 358 but needs power bandwidth up to about 50kHz, and preferably
better O/P drive capability - any suggestions?
Thanks for the reply"ian field" <dai.ode@ntlworld.com> wrote in message
news:jTibh.770$GF5.455@newsfe2-gui.ntli.net...
Something I want to build with an OP-amp needs the "ground sensing"
inputs like the 358 but needs power bandwidth up to about 50kHz, and
preferably better O/P drive capability - any suggestions?
"ground sensing" is quoted directly from one of the '358 datasheets I've"Ground sensing"? I think what you mean is that the input common mode
range extends to the negative supply rail (that is, to "ground" in a
single supply scenario), and the output also can reach the negative rail.
That's what the manufacturers typically mean when they call something a
"single supply" opamp.
Rail to rail might be handy as I want to drive a squarewave into the gate ofThere are plenty of single-supply opamps out there that can do this, as
well as plenty of "rail to rail" opamps that can reach both the negative
and the positive supply. Just use the parametric search functions for the
web site of whatever manufacturer you're fond of.
It's to drive a squarewave and in this application a little ringing isn'tIf you go for a rail-to-rail opamp as opposed to a single-supply opamp, be
aware that they can sometimes be less stable than "traditional" opamps.
If sensing to the negative rail is all you need, you're probably better
off with single-supply.
I've used a CA3140 with positive feedback to make sharp rise/fall times.It's to drive a squarewave and in this application a little ringing
isn't that serious a problem - if it rings less than the discrete
design I'm using I'll be happy!
A fast comparator with rail to rail O/P might do, but so far I've not
found anything suitable in the catalogues I have to hand.
Can it deliver rail to rail O/P to the gate capacitance of a small MOSFET"ian field" <dai.ode@ntlworld.com> wrote in
news:rTCch.1964$GF5.769@newsfe2-gui.ntli.net:
It's to drive a squarewave and in this application a little ringing
isn't that serious a problem - if it rings less than the discrete
design I'm using I'll be happy!
A fast comparator with rail to rail O/P might do, but so far I've not
found anything suitable in the catalogues I have to hand.
I've used a CA3140 with positive feedback to make sharp rise/fall times.
Fast and accurate enough for feeding into a PLL XOR comparator input in
the
audio range, anyway. I chose the CA3140 because it will swing fully to
zero
to allow single supply, use low current input, and be fast.
No idea, it's cheaper to try one if you have one around, than to agoniseI've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Can it deliver rail to rail O/P to the gate capacitance of a small
MOSFET with single supply down to 5.4V at frequencies upto about 50kHz
?
Maybe I'll have a look in my chip tin see if I have one to try, otherwise"ian field" <dai.ode@ntlworld.com> wrote in
news:z2Ech.1067$3S1.183@newsfe1-gui.ntli.net:
I've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Can it deliver rail to rail O/P to the gate capacitance of a small
MOSFET with single supply down to 5.4V at frequencies upto about 50kHz
?
No idea, it's cheaper to try one if you have one around, than to agonise
over it, probably. It has 10 mA output drive, a 9V/ľs slew rate, and is
rated for over 3.5 MHz use, so even at reduced supply voltage it ought to
get by at ultrasonic frequencies. The positive feedback will accelerate
the
slew to overcome momentary lows while charging a capacitance.
It can't do rail to rail, but that wasn't what you asked, at first. It can
get within 0.6V though. Whether this is enough I don't know, it's probably
best to try unless there is a specific reason not to.
Don't buy anything from Maplins. My broadband started to go slow and my"Lostgallifreyan" <no-one@nowhere.net> wrote in message
news:Xns988EC2557356zoodlewurdle@140.99.99.130...
"ian field" <dai.ode@ntlworld.com> wrote in
news:z2Ech.1067$3S1.183@newsfe1-gui.ntli.net:
I've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Can it deliver rail to rail O/P to the gate capacitance of a small
MOSFET with single supply down to 5.4V at frequencies upto about 50kHz
?
No idea, it's cheaper to try one if you have one around, than to agonise
over it, probably. It has 10 mA output drive, a 9V/ľs slew rate, and is
rated for over 3.5 MHz use, so even at reduced supply voltage it ought to
get by at ultrasonic frequencies. The positive feedback will accelerate
the
slew to overcome momentary lows while charging a capacitance.
It can't do rail to rail, but that wasn't what you asked, at first. It can
get within 0.6V though. Whether this is enough I don't know, it's probably
best to try unless there is a specific reason not to.
Maybe I'll have a look in my chip tin see if I have one to try, otherwise
I'm not even going to bother checking if Maplin carry them until they send
me another promotion leaflet with money off vouchers. The discrete design
isn't so bad but I ran out of E-line ZTX transistors and TO92 equivalents
take more space!
Don't buy anything from Maplins. My broadband started to go slow and my"Lostgallifreyan" <no-one@nowhere.net> wrote in message
news:Xns988EC2557356zoodlewurdle@140.99.99.130...
"ian field" <dai.ode@ntlworld.com> wrote in
news:z2Ech.1067$3S1.183@newsfe1-gui.ntli.net:
I've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Can it deliver rail to rail O/P to the gate capacitance of a small
MOSFET with single supply down to 5.4V at frequencies upto about 50kHz
?
No idea, it's cheaper to try one if you have one around, than to agonise
over it, probably. It has 10 mA output drive, a 9V/ľs slew rate, and is
rated for over 3.5 MHz use, so even at reduced supply voltage it ought
to
get by at ultrasonic frequencies. The positive feedback will accelerate
the
slew to overcome momentary lows while charging a capacitance.
It can't do rail to rail, but that wasn't what you asked, at first. It
can
get within 0.6V though. Whether this is enough I don't know, it's
probably
best to try unless there is a specific reason not to.
Maybe I'll have a look in my chip tin see if I have one to try, otherwise
I'm not even going to bother checking if Maplin carry them until they send
me another promotion leaflet with money off vouchers. The discrete design
isn't so bad but I ran out of E-line ZTX transistors and TO92 equivalents
take more space!
Having had time to seek out the data sheets, the '3130 looks a much better"ian field" <dai.ode@ntlworld.com> wrote in
news:rTCch.1964$GF5.769@newsfe2-gui.ntli.net:
It's to drive a squarewave and in this application a little ringing
isn't that serious a problem - if it rings less than the discrete
design I'm using I'll be happy!
A fast comparator with rail to rail O/P might do, but so far I've not
found anything suitable in the catalogues I have to hand.
I've used a CA3140 with positive feedback to make sharp rise/fall times.
Fast and accurate enough for feeding into a PLL XOR comparator input in
the
audio range, anyway. I chose the CA3140 because it will swing fully to
zero
to allow single supply, use low current input, and be fast.
I hope not! I should look at them more, myself. These two IC's in both"Lostgallifreyan" <no-one@nowhere.net> wrote in message
news:Xns988EB0891AABDzoodlewurdle@140.99.99.130...
"ian field" <dai.ode@ntlworld.com> wrote in
news:rTCch.1964$GF5.769@newsfe2-gui.ntli.net:
It's to drive a squarewave and in this application a little ringing
isn't that serious a problem - if it rings less than the discrete
design I'm using I'll be happy!
A fast comparator with rail to rail O/P might do, but so far I've
not found anything suitable in the catalogues I have to hand.
I've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Having had time to seek out the data sheets, the '3130 looks a much
better choice. Maplin don't list it, I suppose now I want some they're
obsolete!
How about a plain ol' LM393 dual comparator (or the quad LM339)? Cheap asRail to rail might be handy as I want to drive a squarewave into the gate
of a small MOSFET and it needs to run off a 6V SLA [...]
A fast comparator with rail to rail O/P might do, but so far I've not
found anything suitable in the catalogues I have to hand.
Thanks - always open to suggestions, I'll have a look for the sheets for"ian field" <dai.ode@ntlworld.com> wrote in
news:fUgdh.21$HV6.15@newsfe1-gui.ntli.net:
"Lostgallifreyan" <no-one@nowhere.net> wrote in message
news:Xns988EB0891AABDzoodlewurdle@140.99.99.130...
"ian field" <dai.ode@ntlworld.com> wrote in
news:rTCch.1964$GF5.769@newsfe2-gui.ntli.net:
It's to drive a squarewave and in this application a little ringing
isn't that serious a problem - if it rings less than the discrete
design I'm using I'll be happy!
A fast comparator with rail to rail O/P might do, but so far I've
not found anything suitable in the catalogues I have to hand.
I've used a CA3140 with positive feedback to make sharp rise/fall
times. Fast and accurate enough for feeding into a PLL XOR comparator
input in the
audio range, anyway. I chose the CA3140 because it will swing fully
to zero
to allow single supply, use low current input, and be fast.
Having had time to seek out the data sheets, the '3130 looks a much
better choice. Maplin don't list it, I suppose now I want some they're
obsolete!
I hope not! I should look at them more, myself. These two IC's in both
single or dual form, are very standard devices, it's worth placing an
order
for a few. Although they won't be ideal for you in this case, check out
the
LF411/LF412. As a drop-in equivalent to the 417, I find them amazing. Very
good general purpose, and in some cases better than more expensive
dedicated audio types. If I haven't got any, I make it a priority to get
some.