Are small signal npn transistors really so different from one another?

[Spehro Pefhany]

He indicated some possible embarrassment :-(

...Jim Thompson

C'mon Paul. We'll be imagining something really, really stupid. Far
worse than your *actual* circuit, which *almost* works.

I've seen some pretty silly-assed stuff out on the net (particularly
with regard to bias), yours can't be much worse. Probably just have to
add a few Rs and Cs to it to get the bias more independent of the
transistor parameters.

Best regards,
Spehro Pefhany

 

[Jim Thompson]

C'mon Paul. We'll be imagining something really, really stupid. Far
worse than your *actual* circuit, which *almost* works.

I've seen some pretty silly-assed stuff out on the net (particularly
with regard to bias), yours can't be much worse. Probably just have to
add a few Rs and Cs to it to get the bias more independent of the
transistor parameters.

Best regards,
Spehro Pefhany

If I post OT I catch all kinds of flack, setting records for thread
length.

Try to get ON-TOPIC and there are no takers :-(

...Jim Thompson

 

[Walter Harley]

C'mon Paul. We'll be imagining something really, really stupid. Far
worse than your *actual* circuit, which *almost* works.

Plus, if it's a real doozy, you could get immortalized in a "bad ideas"
section in AoE 3ed.

 

[Winfield Hill]

Walter Harley wrote...

Spehro Pefhany wrote ...

Plus, if it's a real doozy, you could get immortalized in a
"bad ideas" section in AoE 3ed.

Indeed. But no names are mentioned. :>)

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Spehro Pefhany]

Walter Harley wrote...

Indeed. But no names are mentioned. :>)

I certainly hope to see the Williams bridge so honored.

Best regards,
Spehro Pefhany

 

[John Woodgate]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <[email protected]>)
about 'Are small signal npn transistors really so different from one
another?', on Tue, 23 Dec 2003:

I certainly hope to see the Williams bridge so honored.

What's a Williams bridge?

 

[Spehro Pefhany]

I read in sci.electronics.design that Spehro Pefhany <speffSNIP@interlog
DOTyou.knowwhat> wrote (in <[email protected]>)
about 'Are small signal npn transistors really so different from one
another?', on Tue, 23 Dec 2003:

I certainly hope to see the Williams bridge so honored.

What's a Williams bridge?

The below circuit, but only when k = 0.50


R R
Vin ---+-/\/\/\/-----+----\/\/\/\/-------+ Vout
| ! !
| ! !\ !
\ --!-\ !
/ ! --------------
RV1= R \<---------------!+/
/ /|\ !/
\ k*R
/ |
| \|/
--+----------------------------------0v

RV1= a pot, overall value R.

k= pot position, varying from 0 to 1.

--
Tony Williams.



Best regards,
Spehro Pefhany

 

[Tony Williams]

The below circuit, but only when k = 0.50

R R
Vin ---+-/\/\/\/-----+----\/\/\/\/-------+ Vout
| ! !
| ! !\ !
\ --!-\ !
/ ! --------------
RV1= R \<---------------!+/
/ /|\ !/
\ k*R
/ |
| \|/
--+----------------------------------0v

RV1= a pot, overall value R.

k= pot position, varying from 0 to 1.

I recognise the circuit, but just can't remember the
topic of the thread it related to.

 

[Fred Bloggs]

I recognise the circuit, but just can't remember the
topic of the thread it related to.

Tuning for maximum CMR?

 

[Winfield Hill]

Spehro Pefhany wrote...

Spehro Pefhany wrote ...

I certainly hope to see the Williams bridge so honored.

What's a Williams bridge?

The below circuit, but only when k = 0.50

R R
Vin ---+-/\/\/\/-----+----\/\/\/\/-------+ Vout
| ! !
| ! !\ !
\ --!-\ !
/ ! --------------
RV1= R \<---------------!+/
/ /|\ !/
\ k*R
/ |
| \|/
--+----------------------------------0v

RV1= a pot, overall value R.
k= pot position, varying from 0 to 1.

Indeed, a variant of AoE figure 4.14 with a variable gain from
-1 to +1, which equals zero for k = 0.5, with zero output. :>)

Why's it called a Williams' bridge? To jazz Tony? Is there an
s.e.d. thread reference?

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Spehro Pefhany]

Indeed, a variant of AoE figure 4.14 with a variable gain from
-1 to +1, which equals zero for k = 0.5, with zero output. :>)
Yes.

Why's it called a Williams' bridge? To jazz Tony?

... to assure his immortality (almost forgot that "t")

Is there an s.e.d. thread reference?

http://groups.google.com/groups?hl=...lm=ZgpTu1AhSik8EwIT%40jmwa.demon.co.uk&rnum=2

Best regards,
Spehro Pefhany

 

[Paul Burridge]

C'mon Paul. We'll be imagining something really, really stupid. Far
worse than your *actual* circuit, which *almost* works.

Sorry chaps, My main computer went tits-up and I've been unable to
connect up for 2 days. But I have revised the design and now believe
it should work okay. Certainly by sitting down and doing the
calculations *first* did the trick. I don't mind posting that one as
it doesn't make me look *too* DUMB. And there is certainly some
modest room for improvement yet, I'm sure...

I'll post it later when I've re-read how to go about it.

 

[Paul Burridge]

I read in sci.electronics.design that John Woodgate <[email protected]
raspam.yuk> wrote (in <[email protected]>) about 'Are
small signal npn transistors really so different from one', on Mon, 22
Dec 2003:

Input coupling capacitor added for clarification.

I'm not sure what you mean by "AC couple a diode" but maybe I
explained it poorly. Here's what I've done in schematic form:




output from
final tranny

||
---------||--------->|--------+-------+
|| | |
| |
| |
+ | .---|
| +-| | Meter
--- +-| |
--- | '---|
| |
| |
| |
| |
+---------------+-------+--------+
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


BTW, diode doubler idea might well be very useful if the sensitivity
is still on the low side. Thanks.

 

[Paul Burridge]

Hello Paul,
you are making things very complicated for yourself.

That's an observation I've heard throughout my life...

Your field strength meter is just a crystal set with a meter
in place of the headphones.
You can have the input of the field strength meter,
tuned or untuned, whatever you wish.
You do not need RF amplifiers at 20 feet range.
If you need RF amplification on the field strength meter
then there is something wrong with your radio control transmitter.

Really?? I'd always assumed those non-amplified ones were only good
for up to about one foot away. It just shows how far out one can be
with guesses.

[rest snipped]
I'll check out the references, thanks, John.

 

[Jim Thompson]

I'm not sure what you mean by "AC couple a diode" but maybe I
explained it poorly. Here's what I've done in schematic form:




output from
final tranny

||
---------||--------->|--------+-------+
|| | |
| |
| |
+ | .---|
| +-| | Meter
--- +-| |
--- | '---|
| |
| |
| |
| |
+---------------+-------+--------+
|
===
GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


BTW, diode doubler idea might well be very useful if the sensitivity
is still on the low side. Thanks.

Think on it... the meter is a resistor. The diode only allows current
flow to the right. What happens to the charge on the input capacitor?

...Jim Thompson

 

[John Woodgate]

I read in sci.electronics.design that Paul Burridge
[email protected]>) about 'Are small signal npn transistors really so
different from one', on Tue, 23 Dec 2003:

 

[James Meyer]

Think on it... the meter is a resistor. The diode only allows current
flow to the right. What happens to the charge on the input capacitor?

...Jim Thompson

I'll be willing to bet that Paul is only doing small-signal AC analysis
in his design. A transient analysis would quickly show up the problem with his
output cap.

Jim

 

[Paul Burridge]

Think on it... the meter is a resistor. The diode only allows current
flow to the right. What happens to the charge on the input capacitor?

D'oh! :-(

 

[Tony Williams]

.. to assure his immortality (almost forgot that "t")

Cheeky Blighter......

Hmm.... maybe go down to the Williams Patent Brick
Outhouse and re-align the High Pressure Effluent
Ejector (patent applied for). With the right subject
(and the right curry) it could perhaps hit Toronto.
Teach him what the phrase "Dropped on, from a great
height" really means.