>
> On Mon, 16 Jan 2012 18:11:03 -0800 (PST), George Herold
> <gherold@teachspin.com> wrote:
>
> >On Jan 16, 9:34 am, Jamie
> ><jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> >> Bill Bowden wrote:
> >> > On Jan 15, 11:40 am, Jamie
> >>
> >> > <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
> >>
> >> > > I don 't understand why you don't see it in the sim?
> >>
> >> > > I see all kinds of problems there.
> >>
> >> > > THe outputs are current modes and the beta on the outputs are
> >> > most
> >> > > likely are not going to match well.
> >>
> >> > > On top of that, LTspice shows the upper output (PNP) going into
> >> > > discontinue state at the cross over. This is going to give you a
> >> > period
> >> > > of what I call a flat liner and 99% sure this is where your cross
> >> > over
> >> > > error is coming from.
> >>
> >> > > Plot the current on R12.
> >>
> >> > > Jamie
> >>
> >> > Yes, I did view the current through R12 which looks normal. The thing
> >> > operates class AB, so only one transistor is on at a time, so a 50%
> >> > discontinuous current is normal. I did improve the distortion using a
> >> > 1458 op-amp in place of the 358. Looks much better now. The problem
> >> > now is I only get 1.5 volts peak into 8 ohms with an 8 volt supply and
> >> > I was trying for 3 volts or more. The HFE figure for the 2N2219A is
> >> > minimum 40 at 500mA or 7.5mA at 300mA. The 120 ohm resistor draws .
> >> > 7/120 = about 6 mA so the op-amp must deliver 13.5 mA and the spec
> >> > sheet says only 10 mA short circuit. So, apparently, it needs higher
> >> > gain transistors or an op-amp with lower output impedance, or both.
> >> > Any ideas?
> >>
> >> > -Bill
> >>
> >> That op-amp does not pull the reals, the 358 will do that effect on the
> >> load side and there by give you more v to bias the transistors.
> >>
> >> I don't think you have a current demand problem, you may have a rail
> >> to rail problem how ever.
> >>
> >> The 1458, as old as it is, still has a lot of usages. The las time I
> >> looked, that op-amp (dual) only provides ~ Vcc-1.5 and Vee-1.5. Here you
> >> have lost 3 volts to start with. This now gives you 5 volts to play with.
> >>
> >> Of course, you really don't want to saturate the amp, so lets assume
> >> you have only 4.5V to work with..
> >>
> >> split that in half, since you looks apparrent you are operating in
> >> Class A state on the output side of the op-amp and you get ~ 2.25 volts
> >> Peak to play with.
> >>
> >> Now., let us not forget, the minimum required for each of those
> >> transistors to start working. ~ 0.7 and then times this by 2 and you get
> >> 1.4. Remove that value off the top and you are now getting closer to
> >> where the problem is.
> >>
> >> That configuration you're using in the first place is fighting against
> >> you. As one side is conducting the other side is still conducting, just
> >> about all the way through. This is going to remove a good chunk of your
> >> output.
> >>
> >> Have you considered a config like the following or something in this line?
> >>
> >> 8Volts-----------------------------+
> >> + |
> >> |
> >> |
> >> +
> >> |<
> >> +-----------------+|
> >> ___ | |\
> >> +--+|___|-+----------------++ |
> >> | | | +
> >> + | | |
> >> || | |\+ | | 1Ku
> >> -||+--++-------------+|-\ | | ||
> >> || | >+-------+----------+---+||+-----+
> >> +-+-|+/ | || |
> >> 4Volts |/+ | +
> >> | | |
> >> | | .-.
> >> | | | |
> >> + + | |8
> >> | |/ '-'
> >> +-----------------+| |
> >> |> GND
> >> +
> >> |
> >> |
> >> ===
> >> GND
> >>
> >> Jamie- Hide quoted text -
> >>
> >> - Show quoted text -
> >
> >That's weird looking too! There's a JL circuit with tran's in the
> >power leads,
> >but I think it's push-pull. You can get a lot closer to the supply
> >rail that way...
> >At least that's my understanding. I've yet to try a circuit with
> >power gain in the supply leads.
> >
> >George H.
>
> I did that sort of thing as an LDO, ~1970... it's in a hybrid I made
> for the TOW missile. You need base-emitter resistors such that the
> "crowbar" current is zero. Disconnect OpAmp output from as shown,
> then connect it via a resistive divider between rails (it'd be a
> single resistor to ground if split supplies were used. It's then a
> CLASS-B amplifier.
>
Connecting the op amp output to the circuit's output via a
suitably-chosen small resistance gives you a nice combination of
feedforward at small signals and output-stage feedback at large
signals. Frequency compensation can be a bit squirrelly.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Reply by krw...@att.bizzzzzzzzzzzz●January 17, 20122012-01-17
On Tue, 17 Jan 2012 22:23:55 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>krw@att.bizzzzzzzzzzzz wrote:
>
>> On Tue, 17 Jan 2012 22:00:36 -0500, Jamie
>> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>>
>>
>>>krw@att.bizzzzzzzzzzzz wrote:
>>>
>>>
>>>>On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>>>>
>>>>
>>>>
>>>>>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>>>>>
>>>>>
>>>>>>On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>>>>
>>>>>>
>>>>>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>>>>>designed 50 years ago... all math... no simulator existed until about
>>>>>>>25 years into my career. Also have some of my chips used as class
>>>>>>>examples at Rochester Institute of Technology.
>>>>>>
>>>>>>25 years? Circuit simulators existed more than 40 years ago.
>>>>>
>>>>>You're assuming Jim's career launched 50 years ago, when upon walking into a
>>>>>firm off the street without a clue, he got a job designing integrated circuits.
>>>>>Then, 25 years later, simulators appeared.
>>>>
>>>>
>>>>Well, he's just about to turn 19 (76 in human years).
>>>>
>>>>
>>>>
>>>>>Indeed, it is quite obvious that a little math around here wouldn't be such a
>>>>>bad thing.
>>>>
>>>>
>>>>You might try it. Unless he started his career before age 11 (76-40-25), I
>>>>doubt his statement. Note that this assumes I used the very first circuit
>>>>simulators, which I highly doubt.
>>>
>>>The only thing I ever did was tried out Verilog and I absolutely hated it..
>>
>>
>> Huh? In English, please.
>>
>>
>>> It may have been greatly improved since then but it just didn't turn
>>>me on.
>>
>>
>> I don't like C, so have never bothered with Verilog. VHDL (and likewise,
>> PL/I) are much more my style.
>>
>>
>>> Being that I also do C, Pascal, Asm etc, you would think that would
>>>just fit in but it didn't.
>>
>>
>> I still don't understand the relevance.
>
> Ok, if you say so.
Yeah, you got me. What does Verilog have to do with circuit simulators? ...or
C, or Pascal, or Asm, or...
Reply by Jim Thompson●January 17, 20122012-01-17
On Tue, 17 Jan 2012 21:52:48 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>Jim Thompson wrote:
>
[snip]
>>
>> Those Youtube videos Bitrex found of IIT lectures are based on chips I
>> designed 50 years ago... all math... no simulator existed until about
>> 25 years into my career. Also have some of my chips used as class
>> examples at Rochester Institute of Technology.
>>
>> Calculate that quiescent current and get back to me with the result.
>> (Show all your work :-)
>>
>> ...Jim Thompson
>I suppose I could, but I don't know where that would lead me to?
Might lead to understanding rather than groping.
>
> In any case, the LT part# I used in the sim was a low quiescent type
>to start with. I am sure as simple as that circuit is, the sim can't be
>that far off. I suppose if you select an opamp that has more than one
>diode drop from the rails it could cause the outputs to have a high
>Qu level. But why would you want to use a op-amp that bad? Infact I
>can't think of one that has more than 1 diode drop on the rails at the
>moment.
>
> And Like I said, proven circuits that are still operating today tells
>me alot..
Naaaah! It tell me the great disaster is about to befall you.
>
> Back in the old days my HP calculator, slide rule and lots of paper
>was my friend. With Polaroid's of scope shots stuffed in scrap books.
>
> Btw
>
> It just came to me, this type of circuit is used to drive a optics
>focus coil current mode amplifier on a 2 Mev irradiation unit. The lower
> NPN is used to suppress the reactive energy when throttling back
>instead of using a snubber or diode, this keeps it symmetrical when we
>turn off the mag field to avoid unexpected beam steering. That uses a
>large power
>IC audio amplifier with the base of the transistors in the rails of the
> IC with some by pass R to set the Qu I.
>
>Jamie
Stay awake tonight... your end is near ;-)
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Reply by Jim Thompson●January 17, 20122012-01-17
On Tue, 17 Jan 2012 22:00:36 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>krw@att.bizzzzzzzzzzzz wrote:
>
>> On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>>
>>
>>>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>>>
>>>>On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>>
>>>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>>>designed 50 years ago... all math... no simulator existed until about
>>>>>25 years into my career. Also have some of my chips used as class
>>>>>examples at Rochester Institute of Technology.
>>>>
>>>>25 years? Circuit simulators existed more than 40 years ago.
>>>
>>>You're assuming Jim's career launched 50 years ago, when upon walking into a
>>>firm off the street without a clue, he got a job designing integrated circuits.
>>>Then, 25 years later, simulators appeared.
>>
>>
>> Well, he's just about to turn 19 (76 in human years).
Please! I'm turning 18 ;-)
>>
>>
>>>Indeed, it is quite obvious that a little math around here wouldn't be such a
>>>bad thing.
>>
>>
>> You might try it. Unless he started his career before age 11 (76-40-25), I
>> doubt his statement. Note that this assumes I used the very first circuit
>> simulators, which I highly doubt.
>The only thing I ever did was tried out Verilog and I absolutely hated it..
>
> It may have been greatly improved since then but it just didn't turn
>me on.
>
> Being that I also do C, Pascal, Asm etc, you would think that would
>just fit in but it didn't.
>
>Jamie
>
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Reply by Jamie●January 17, 20122012-01-17
krw@att.bizzzzzzzzzzzz wrote:
> On Tue, 17 Jan 2012 22:00:36 -0500, Jamie
> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>
>
>>krw@att.bizzzzzzzzzzzz wrote:
>>
>>
>>>On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>>>
>>>
>>>
>>>>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>>>>
>>>>
>>>>>On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>>>
>>>>>
>>>>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>>>>designed 50 years ago... all math... no simulator existed until about
>>>>>>25 years into my career. Also have some of my chips used as class
>>>>>>examples at Rochester Institute of Technology.
>>>>>
>>>>>25 years? Circuit simulators existed more than 40 years ago.
>>>>
>>>>You're assuming Jim's career launched 50 years ago, when upon walking into a
>>>>firm off the street without a clue, he got a job designing integrated circuits.
>>>>Then, 25 years later, simulators appeared.
>>>
>>>
>>>Well, he's just about to turn 19 (76 in human years).
>>>
>>>
>>>
>>>>Indeed, it is quite obvious that a little math around here wouldn't be such a
>>>>bad thing.
>>>
>>>
>>>You might try it. Unless he started his career before age 11 (76-40-25), I
>>>doubt his statement. Note that this assumes I used the very first circuit
>>>simulators, which I highly doubt.
>>
>>The only thing I ever did was tried out Verilog and I absolutely hated it..
>
>
> Huh? In English, please.
>
>
>> It may have been greatly improved since then but it just didn't turn
>>me on.
>
>
> I don't like C, so have never bothered with Verilog. VHDL (and likewise,
> PL/I) are much more my style.
>
>
>> Being that I also do C, Pascal, Asm etc, you would think that would
>>just fit in but it didn't.
>
>
> I still don't understand the relevance.
Ok, if you say so.
Jamie
Reply by krw...@att.bizzzzzzzzzzzz●January 17, 20122012-01-17
On Tue, 17 Jan 2012 22:00:36 -0500, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>krw@att.bizzzzzzzzzzzz wrote:
>
>> On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>>
>>
>>>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>>>
>>>>On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>>
>>>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>>>designed 50 years ago... all math... no simulator existed until about
>>>>>25 years into my career. Also have some of my chips used as class
>>>>>examples at Rochester Institute of Technology.
>>>>
>>>>25 years? Circuit simulators existed more than 40 years ago.
>>>
>>>You're assuming Jim's career launched 50 years ago, when upon walking into a
>>>firm off the street without a clue, he got a job designing integrated circuits.
>>>Then, 25 years later, simulators appeared.
>>
>>
>> Well, he's just about to turn 19 (76 in human years).
>>
>>
>>>Indeed, it is quite obvious that a little math around here wouldn't be such a
>>>bad thing.
>>
>>
>> You might try it. Unless he started his career before age 11 (76-40-25), I
>> doubt his statement. Note that this assumes I used the very first circuit
>> simulators, which I highly doubt.
>The only thing I ever did was tried out Verilog and I absolutely hated it..
Huh? In English, please.
> It may have been greatly improved since then but it just didn't turn
>me on.
I don't like C, so have never bothered with Verilog. VHDL (and likewise,
PL/I) are much more my style.
> Being that I also do C, Pascal, Asm etc, you would think that would
>just fit in but it didn't.
I still don't understand the relevance.
Reply by Jamie●January 17, 20122012-01-17
krw@att.bizzzzzzzzzzzz wrote:
> On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>
>
>>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>>
>>>On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>
>>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>>designed 50 years ago... all math... no simulator existed until about
>>>>25 years into my career. Also have some of my chips used as class
>>>>examples at Rochester Institute of Technology.
>>>
>>>25 years? Circuit simulators existed more than 40 years ago.
>>
>>You're assuming Jim's career launched 50 years ago, when upon walking into a
>>firm off the street without a clue, he got a job designing integrated circuits.
>>Then, 25 years later, simulators appeared.
>
>
> Well, he's just about to turn 19 (76 in human years).
>
>
>>Indeed, it is quite obvious that a little math around here wouldn't be such a
>>bad thing.
>
>
> You might try it. Unless he started his career before age 11 (76-40-25), I
> doubt his statement. Note that this assumes I used the very first circuit
> simulators, which I highly doubt.
The only thing I ever did was tried out Verilog and I absolutely hated it..
It may have been greatly improved since then but it just didn't turn
me on.
Being that I also do C, Pascal, Asm etc, you would think that would
just fit in but it didn't.
Jamie
Reply by Jamie●January 17, 20122012-01-17
Jim Thompson wrote:
> On Tue, 17 Jan 2012 17:57:06 -0500, Jamie
> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>
>
>>Jim Thompson wrote:
>>
>>
>>>On Mon, 16 Jan 2012 19:59:06 -0500, Jamie
>>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>>>
>>>
>>>
>>>>Jim Thompson wrote:
>>>>
>>>>
>>>>
>>>>>On Mon, 16 Jan 2012 19:07:38 -0500, Jamie
>>>>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>Jim Thompson wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>On Mon, 16 Jan 2012 09:34:51 -0500, Jamie
>>>>>>><jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>>Bill Bowden wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>>On Jan 15, 11:40 am, Jamie
>>>>>>>>>
>>>>>>>>><jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>I don 't understand why you don't see it in the sim?
>>>>>>>>>>
>>>>>>>>>>I see all kinds of problems there.
>>>>>>>>>>
>>>>>>>>>>THe outputs are current modes and the beta on the outputs are
>>>>>>>>>
>>>>>>>>>most
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>likely are not going to match well.
>>>>>>>>>>
>>>>>>>>>> On top of that, LTspice shows the upper output (PNP) going into
>>>>>>>>>>discontinue state at the cross over. This is going to give you a
>>>>>>>>>
>>>>>>>>>period
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>of what I call a flat liner and 99% sure this is where your cross
>>>>>>>>>
>>>>>>>>>over
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>>error is coming from.
>>>>>>>>>>
>>>>>>>>>>Plot the current on R12.
>>>>>>>>>>
>>>>>>>>>>Jamie
>>>>>>>>>
>>>>>>>>>Yes, I did view the current through R12 which looks normal. The thing
>>>>>>>>>operates class AB, so only one transistor is on at a time, so a 50%
>>>>>>>>>discontinuous current is normal. I did improve the distortion using a
>>>>>>>>>1458 op-amp in place of the 358. Looks much better now. The problem
>>>>>>>>>now is I only get 1.5 volts peak into 8 ohms with an 8 volt supply and
>>>>>>>>>I was trying for 3 volts or more. The HFE figure for the 2N2219A is
>>>>>>>>>minimum 40 at 500mA or 7.5mA at 300mA. The 120 ohm resistor draws .
>>>>>>>>>7/120 = about 6 mA so the op-amp must deliver 13.5 mA and the spec
>>>>>>>>>sheet says only 10 mA short circuit. So, apparently, it needs higher
>>>>>>>>>gain transistors or an op-amp with lower output impedance, or both.
>>>>>>>>>Any ideas?
>>>>>>>>>
>>>>>>>>>-Bill
>>>>>>>>
>>>>>>>>That op-amp does not pull the reals, the 358 will do that effect on the
>>>>>>>>load side and there by give you more v to bias the transistors.
>>>>>>>>
>>>>>>>>I don't think you have a current demand problem, you may have a rail
>>>>>>>>to rail problem how ever.
>>>>>>>>
>>>>>>>>The 1458, as old as it is, still has a lot of usages. The las time I
>>>>>>>>looked, that op-amp (dual) only provides ~ Vcc-1.5 and Vee-1.5. Here you
>>>>>>>>have lost 3 volts to start with. This now gives you 5 volts to play with.
>>>>>>>>
>>>>>>>>Of course, you really don't want to saturate the amp, so lets assume
>>>>>>>>you have only 4.5V to work with..
>>>>>>>>
>>>>>>>>split that in half, since you looks apparrent you are operating in
>>>>>>>>Class A state on the output side of the op-amp and you get ~ 2.25 volts
>>>>>>>>Peak to play with.
>>>>>>>>
>>>>>>>>Now., let us not forget, the minimum required for each of those
>>>>>>>>transistors to start working. ~ 0.7 and then times this by 2 and you get
>>>>>>>>1.4. Remove that value off the top and you are now getting closer to
>>>>>>>>where the problem is.
>>>>>>>>
>>>>>>>>That configuration you're using in the first place is fighting against
>>>>>>>>you. As one side is conducting the other side is still conducting, just
>>>>>>>>about all the way through. This is going to remove a good chunk of your
>>>>>>>>output.
>>>>>>>>
>>>>>>>>Have you considered a config like the following or something in this line?
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> 8Volts-----------------------------+
>>>>>>>> + |
>>>>>>>> |
>>>>>>>> |
>>>>>>>> +
>>>>>>>> |<
>>>>>>>> +-----------------+|
>>>>>>>> ___ | |\
>>>>>>>> +--+|___|-+----------------++ |
>>>>>>>> | | | +
>>>>>>>> + | | |
>>>>>>>> || | |\+ | | 1Ku
>>>>>>>> -||+--++-------------+|-\ | | ||
>>>>>>>> || | >+-------+----------+---+||+-----+
>>>>>>>> +-+-|+/ | || |
>>>>>>>> 4Volts |/+ | +
>>>>>>>> | | |
>>>>>>>> | | .-.
>>>>>>>> | | | |
>>>>>>>> + + | |8
>>>>>>>> | |/ '-'
>>>>>>>> +-----------------+| |
>>>>>>>> |> GND
>>>>>>>> +
>>>>>>>> |
>>>>>>>> |
>>>>>>>> ===
>>>>>>>> GND
>>>>>>>>
>>>>>>>>
>>>>>>>>Jamie
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>What sets the quiescent current thru the PNP-NPN path?
>>>>>>>
>>>>>>> ...Jim Thompson
>>>>>>
>>>>>>The quiescent I of the op-amp and load.
>>>>>>
>>>>>>In Ltspice it was ~ 70 ma with that basic circuit in both
>>>>>>the PNP and NPN. I was using 700..800 ma trannies.
>>>>>>
>>>>>>Putting an R between Vcc and B of the PNP will drop that down
>>>>>>a bit and bring it closer to being symmetrical. Also, you can
>>>>>>use a R on the op output to the collector bridge to lower the
>>>>>>Quies.
>>>>>>
>>>>>>I Didn't save the spice I used but I am sure I can put it together
>>>>>>again and post it if you wish, I just used what was in the stock lib.
>>>>>>
>>>>>>
>>>>>>Jamie
>>>>>>
>>>>>
>>>>>
>>>>>Try it in the real world. Have lots of spare transistors on hand :-)
>>>>>
>>>>> ...Jim Thompson
>>>>
>>>>Actually Jim, I have done that in real world cases. Which is why I
>>>>suggested it.. It does work when you use the correct set of components
>>>>and is a basic of many designs that i've seen over the years. A very
>>>>particle way to having current outputs
>>>>
>>>> Old time 741 with Emitter outputs and related type power amp Ic's
>>>>work very nicely with a config like that. Of course in many cases, you
>>>>need to tailor the bias a little with some bypass R's on the Rail to the
>>>>base of each side if the Qu current is too high.
>>>>
>>>> I had a load of LM380's years ago that I put to some good use making
>>>>little half bridge servos with a circuit of that type.
>>>>
>>>> The only problem with that design is, if the driving op-amp happens
>>>>to circuit for some reason. It will take out the outputs. A current
>>>>limiting R on the op-amp output to the collector node is a good
>>>>practice, something I did not use here in this example. And don't forget
>>>>the bypass bias R's incase the QU Is too high in the chip that is used.
>>>>
>>>>
>>>>I know your an old pro and I am sure you have had your share of
>>>>smoking some silicon. :)
>>>>
>>>>Jamie
>>>>
>>>
>>>
>>>Larkin will bless your work. Me? I do not recommend it... do
>>>yourself a favor and do some Algebra. On a job interview I'd toss
>>>your ass in a blink ;-)
>>>
>>> ...Jim Thompson
>>
>> Jim, I don't need to, I've assembled circuits like that, that are still
>>operating today.
>
>
> OK. Show me your math. What's the quiescent current thru the PNP-NPN
> path?
>
>
>> You can toss my ass all you want, all it will get you is a bad back..
>>
>> P.S.
>> I never used a simulator all these years until recently, my math
>>skills have served me well.
>>
>>Jamie
>>
>
>
> Those Youtube videos Bitrex found of IIT lectures are based on chips I
> designed 50 years ago... all math... no simulator existed until about
> 25 years into my career. Also have some of my chips used as class
> examples at Rochester Institute of Technology.
>
> Calculate that quiescent current and get back to me with the result.
> (Show all your work :-)
>
> ...Jim Thompson
I suppose I could, but I don't know where that would lead me to?
In any case, the LT part# I used in the sim was a low quiescent type
to start with. I am sure as simple as that circuit is, the sim can't be
that far off. I suppose if you select an opamp that has more than one
diode drop from the rails it could cause the outputs to have a high
Qu level. But why would you want to use a op-amp that bad? Infact I
can't think of one that has more than 1 diode drop on the rails at the
moment.
And Like I said, proven circuits that are still operating today tells
me alot..
Back in the old days my HP calculator, slide rule and lots of paper
was my friend. With Polaroid's of scope shots stuffed in scrap books.
Btw
It just came to me, this type of circuit is used to drive a optics
focus coil current mode amplifier on a 2 Mev irradiation unit. The lower
NPN is used to suppress the reactive energy when throttling back
instead of using a snubber or diode, this keeps it symmetrical when we
turn off the mag field to avoid unexpected beam steering. That uses a
large power
IC audio amplifier with the base of the transistors in the rails of the
IC with some by pass R to set the Qu I.
Jamie
Reply by krw...@att.bizzzzzzzzzzzz●January 17, 20122012-01-17
On Wed, 18 Jan 2012 01:18:41 +0000 (UTC), Kaz Kylheku <kaz@kylheku.com> wrote:
>On 2012-01-18, krw@att.bizzzzzzzzzzzz <krw@att.bizzzzzzzzzzzz> wrote:
>> On Tue, 17 Jan 2012 16:23:22 -0700, Jim Thompson
>>>Those Youtube videos Bitrex found of IIT lectures are based on chips I
>>>designed 50 years ago... all math... no simulator existed until about
>>>25 years into my career. Also have some of my chips used as class
>>>examples at Rochester Institute of Technology.
>>
>> 25 years? Circuit simulators existed more than 40 years ago.
>
>You're assuming Jim's career launched 50 years ago, when upon walking into a
>firm off the street without a clue, he got a job designing integrated circuits.
>Then, 25 years later, simulators appeared.
Well, he's just about to turn 19 (76 in human years).
>Indeed, it is quite obvious that a little math around here wouldn't be such a
>bad thing.
You might try it. Unless he started his career before age 11 (76-40-25), I
doubt his statement. Note that this assumes I used the very first circuit
simulators, which I highly doubt.
Reply by Jamie●January 17, 20122012-01-17
Bill Bowden wrote:
> On Jan 16, 6:34 am, Jamie
> <jamie_ka1lpa_not_valid_after_ka1l...@charter.net> wrote:
>
> > That op-amp does not pull the reals, the 358 will do that effect
> on the
> > load side and there by give you more v to bias the transistors.
> >
> > I don't think you have a current demand problem, you may have a
> rail
> > to rail problem how ever.
> >
> > The 1458, as old as it is, still has a lot of usages. The las
> time I
> > looked, that op-amp (dual) only provides ~ Vcc-1.5 and Vee-1.5.
> Here you
> > have lost 3 volts to start with. This now gives you 5 volts to play
> with.
> >
>
> Why would the op-amp rail to rail limit be a consideration? Imagine
> the transistors have a large HFE of say 1000. There will be a large
> voltage gain from the op-amp output to the main output. If the main
> output is moving rail to rail, the op-amp output will be moving much
> less, maybe only 1 volt or so.
>
> -Bill
Because you loss the dynamic range of voltage you need to work with.
High gain units of around 1000 or more are typically darlington and even
suffer from a worse faith in your case. More 2 or more diode drops of
voltage.
Consider the schematic below for an idea. THis uses 2 NPN for outputs.
This suffers from 2 diode drops only. One from the upper NPN and one
from the Op-amp if you don't have a rail type. Of course, if you want to
use a couple of inverting units at the top you can bring it down to 1
diode drop.
8 Volt Rail
+-------------------------+
|
|
+
|/
Op-Amp out put +--------+-------------+| NPN
+ |>
| +
V 1n914 | <-- Minus Feed back
- |
| | ||
| +-----+-||+---+
V 1n914 | || |
- | |
| +--------+ .-.
| |< | | |
+-+-+-| PNP | | | 8
| |\ + '-'
+ + |/ |
.-. +-----+| NPN
| | |> GND
10k | | +
'-' |
+ |
| +
| |
G+D G+D
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Jamie