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simple opamp amplifier circuit

Started by panfilero June 18, 2012
On 6/18/2012 11:05 AM, panfilero wrote:
> On Monday, June 18, 2012 9:37:27 AM UTC-5, Fred Bartoli wrote: >> panfilero a �crit : >>> I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the rails... why is this? The link shows what I'm doing in LTSpice >>> >>> thanks >>> >>> http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg >>> >> >> Assuming your DC input is 0V, then the circuit has a gain of 3 WRT to >> the opamp positive input and the 3x2.5V = 7.5V hits the rail. >> >> Do you really need simulation for that? >> >> -- >> Thanks, >> Fred. > > what's WRT?
'With Respect To'
bloggs.fredbloggs.fred@gmail.com a �crit :
> On Monday, June 18, 2012 10:37:27 AM UTC-4, Fred Bartoli wrote: >> panfilero a �crit : >>> I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offset, but if I don't include a capacitor on my input my output hits the rails... why is this? The link shows what I'm doing in LTSpice >>> >>> thanks >>> >>> http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg >>> >> Assuming your DC input is 0V, then the circuit has a gain of 3 WRT to >> the opamp positive input and the 3x2.5V = 7.5V hits the rail. >> >> Do you really need simulation for that? >> >> -- >> Thanks, >> Fred. > > huh?
(huh?)? Huh? :-) -- Thanks, Fred.
"Jon Elson"
>> >> http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg > > This circuit has a 2:1 DC gain ...
** Nope - the schem as shown has a DC gain of zero. Without C1 ( and R2 grounded) it has a DC gain of 3, so the 2.5 volt fixed input drives to op-amp to the 5V rail. The "pan fried sandwich" is a colossal idiot. And you are no better. .... Phil
Try centering the input around 2.5V instead of 0 volts
<rcmonsen@gmail.com> wrote in message 
news:1771316b-c27b-4469-8741-9bbf95b81f9a@googlegroups.com...
> Try centering the input around 2.5V instead of 0 volts
Good suggestion, bump the offset in the sig gen to 2.5V
Dennis wrote:
> <rcmonsen@gmail.com> wrote in message > news:1771316b-c27b-4469-8741-9bbf95b81f9a@googlegroups.com... > >>Try centering the input around 2.5V instead of 0 volts > > > Good suggestion, bump the offset in the sig gen to 2.5V > >
Why not use a dual rail supply, virtual ground or a (-) regulated DC-DC simple converter on board to supply the (-) rail? Jamie
On 6/18/2012 2:59 PM, Phil Allison wrote:
> "Jon Elson" >>> >>> http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg >> >> This circuit has a 2:1 DC gain ... > > > ** Nope - the schem as shown has a DC gain of zero. > > Without C1 ( and R2 grounded) it has a DC gain of 3, so the 2.5 volt fixed > input drives to op-amp to the 5V rail. > > The "pan fried sandwich" is a colossal idiot. > > And you are no better. > > > .... Phil > > > >
When learning, you need to start somewhere. I see no reason to insult the original poster. Everyone else managed to be civilized.
"miso = Cunthead"

>> The "pan fried sandwich" is a colossal idiot. >> >> And you are no better. >> > > When learning, you need to start somewhere.
** When bullshitting - you need to know when to stop.
> I see no reason...
** That alone is true, the rest is purest bullshit. Fuck off - you bloody troll. ... Phil
On Jun 18, 4:03=A0pm, panfilero <panfil...@gmail.com> wrote:
> On Monday, June 18, 2012 9:25:39 AM UTC-5, panfilero wrote: > > I'm simulating on LTSpice, a simple amplifier circuit with a 2.5V offse=
t, but if I don't include a capacitor on my input my output hits the rails.= .. why is this? =A0The link shows what I'm doing in LTSpice
> > > thanks > > >http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg > > sorry, the input signal is a sine wave, with no dc offset, at 10kHz with =
0.25V amplitude Input signal has zero offset, opamp has half Vrail offset. Problem. NT
On Tue, 19 Jun 2012 07:59:16 +1000, "Phil Allison" <phil_a@tpg.com.au>
wrote:

> >"Jon Elson" >>> >>> http://i555.photobucket.com/albums/jj477/panfilero/Capture-1.jpg >> >> This circuit has a 2:1 DC gain ... > > >** Nope - the schem as shown has a DC gain of zero. > >Without C1 ( and R2 grounded) it has a DC gain of 3, so the 2.5 volt fixed >input drives to op-amp to the 5V rail. > >The "pan fried sandwich" is a colossal idiot. > >And you are no better. > > >.... Phil > > >
On my planet, the DC gain relative to 2.5V (without C) would be -R1/R2. i.e. -2x. I know, it is hard..