Ramp Type Oscillator with Bottom Release

Started by Jim Thompson September 13, 2017
Ramp Type Oscillator with Bottom Release

In the past I did this (in bipolar), so that I got a near-zero release
of the "dump" function by sensing saturation...

<http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf>

... easy with bipolar devices.

Any ideas on how to do it similarly with CMOS?

(Comparators sensing near zero are risky with CMOS due to crappy
offset voltages.)

For the leftists in the crowd (too high a percentage ;-) this IS
ON-TOPIC.
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

             I'm looking for work... see my website.

Thinking outside the box...producing elegant & economic solutions.
On Wednesday, September 13, 2017 at 4:20:22 PM UTC-4, Jim Thompson wrote:
> Ramp Type Oscillator with Bottom Release > > In the past I did this (in bipolar), so that I got a near-zero release > of the "dump" function by sensing saturation... > > <http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf> > > ... easy with bipolar devices. > > Any ideas on how to do it similarly with CMOS? > > (Comparators sensing near zero are risky with CMOS due to crappy > offset voltages.)
Run it into some edge and sense dV/dt. (?) George H.
> > For the leftists in the crowd (too high a percentage ;-) this IS > ON-TOPIC. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I'm looking for work... see my website. > > Thinking outside the box...producing elegant & economic solutions.
What's wrong with doing it exactly the same way?

Gm is smaller so you need more gain on the resulting current signal.  You're 
making a kind of comparison, regardless.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in 
message news:if4jrc1joa2mm0n6a1hjjuoe7eaknb24t2@4ax.com...
> Ramp Type Oscillator with Bottom Release > > In the past I did this (in bipolar), so that I got a near-zero release > of the "dump" function by sensing saturation... > > <http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf> > > ... easy with bipolar devices. > > Any ideas on how to do it similarly with CMOS? > > (Comparators sensing near zero are risky with CMOS due to crappy > offset voltages.) > > For the leftists in the crowd (too high a percentage ;-) this IS > ON-TOPIC. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I'm looking for work... see my website. > > Thinking outside the box...producing elegant & economic solutions.
On 09/13/2017 04:20 PM, Jim Thompson wrote:
> Ramp Type Oscillator with Bottom Release > > In the past I did this (in bipolar), so that I got a near-zero release > of the "dump" function by sensing saturation... > > <http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf> > > ... easy with bipolar devices. > > Any ideas on how to do it similarly with CMOS? > > (Comparators sensing near zero are risky with CMOS due to crappy > offset voltages.)
So don't use it to sense the cap voltage directly against a voltage reference that's near the rail. Make a copy of mirror/CCS Q7 and its resistor that just sends current to ground (or use it as the load for Q2), and sense charging current differentially wrt to the reference mirror, from the source resistor/source junctions. By adjusting the emitter resistor ratio you should be able to set the "trip point" anywhere you like...
> For the leftists in the crowd (too high a percentage ;-) this IS > ON-TOPIC. > > ...Jim Thompson >
Yay!
On 09/14/2017 07:47 AM, bitrex wrote:
> On 09/13/2017 04:20 PM, Jim Thompson wrote: >> Ramp Type Oscillator with Bottom Release >> >> In the past I did this (in bipolar), so that I got a near-zero release >> of the "dump" function by sensing saturation... >> >> <http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf> >> >> >> ... easy with bipolar devices. >> >> Any ideas on how to do it similarly with CMOS? >> >> (Comparators sensing near zero are risky with CMOS due to crappy >> offset voltages.) > > So don't use it to sense the cap voltage directly against a voltage > reference that's near the rail. Make a copy of mirror/CCS Q7 and its > resistor that just sends current to ground (or use it as the load for > Q2)
Q4, rather
On 2017-09-13 13:20, Jim Thompson wrote:
> Ramp Type Oscillator with Bottom Release > > In the past I did this (in bipolar), so that I got a near-zero release > of the "dump" function by sensing saturation... > > <http://www.analog-innovations.com/SED/RampGenerator_ChryslerIgnition.pdf> > > ... easy with bipolar devices. > > Any ideas on how to do it similarly with CMOS? >
Can you run a little charge pump with mux in there so a tiny capacitance gets charged up to a bandgap and then added to zero? That way you should be able get even closer to zero than with you bipolar circuit.
> (Comparators sensing near zero are risky with CMOS due to crappy > offset voltages.) > > For the leftists in the crowd (too high a percentage ;-) this IS > ON-TOPIC. >
However, you used the word "dump", which is similar to the word "fired", which ... :-) -- Regards, Joerg http://www.analogconsultants.com/
On Thu, 14 Sep 2017 05:39:07 -0500, "Tim Williams"
<tmoranwms@gmail.com> wrote:

>What's wrong with doing it exactly the same way? > >Gm is smaller so you need more gain on the resulting current signal. You're >making a kind of comparison, regardless. > >Tim
The "way" detected the jump in Ib. No such current exists in CMOS. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box...producing elegant & economic solutions.
"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in 
message news:sq6lrcla5gr2nqsklripoa3ljdbb1hf00b@4ax.com...
> The "way" detected the jump in Ib. No such current exists in CMOS. >
So? Fake a BJT by adding a diode-strapped MOS in parallel with it? Add a diode-strapped MOS from gate to drain (Baker clamp, in a sense)? Bias it up with diode-strapped-MOS's so you're not comparing against zero? You tell me, you're the self-proclaimed expert. I thought only liberals wanted hand-outs. ;-) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
On 09/14/2017 04:48 PM, Tim Williams wrote:
> "Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote > in message news:sq6lrcla5gr2nqsklripoa3ljdbb1hf00b@4ax.com... >> The "way" detected the jump in Ib. No such current exists in CMOS. >> > > So? Fake a BJT by adding a diode-strapped MOS in parallel with it? Add > a diode-strapped MOS from gate to drain (Baker clamp, in a sense)? > > Bias it up with diode-strapped-MOS's so you're not comparing against zero? > > You tell me, you're the self-proclaimed expert. I thought only liberals > wanted hand-outs. ;-) > > Tim >
I'm curious as to what Chrysler the BJT version was for
On Thu, 14 Sep 2017 15:48:23 -0500, "Tim Williams"
<tmoranwms@gmail.com> wrote:

>"Jim Thompson" <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote in >message news:sq6lrcla5gr2nqsklripoa3ljdbb1hf00b@4ax.com... >> The "way" detected the jump in Ib. No such current exists in CMOS. >> > >So? Fake a BJT by adding a diode-strapped MOS in parallel with it? Add a >diode-strapped MOS from gate to drain (Baker clamp, in a sense)? > >Bias it up with diode-strapped-MOS's so you're not comparing against zero? > >You tell me, you're the self-proclaimed expert. I thought only liberals >wanted hand-outs. ;-) > >Tim
Fricking amateur. Plonk. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box...producing elegant & economic solutions.