Driver to drive?

On Friday, April 4, 2014 8:56:19 AM UTC-4, George Herold wrote:

On Thursday, April 3, 2014 11:57:57 PM UTC-4, Sylvia Else wrote:

On 4/04/2014 12:48 PM, Jim Thompson wrote:



On Thu, 03 Apr 2014 18:40:39 +1100, Sylvia Else

...Jim Thompson







Thanks.



After looking at some stuff relating to solving simultaneous 1st order

differential equations, I learnt that two first order simultaneous

equations in two variables can be written as a single second order

differential equation in one variable, which I do know how to solve.





So I went back, and saw how that could be achieved



The result is a rather involved function of the six variables (C1, C2,

R1, R2, V1 and V2).



This is not actually an electronic circuit, but a representation of the

thermal behaviour of a water heater. Consequently I don't know the

values of V1, C1 or R1. I was hoping to infer them from the equation and

the measured behaviour. I'd end up with three simultaneous equations to

solve, which, given their complexity, would probably have to be done

numerically.



Ahh I've done that. Usually you can stare at it and find one RC that dominates the behavior. You'll want to model the heater as a current source.

Temperature corresponds to voltage and Energy is like charge. So a one watt heater is like a 1 amp current source.

The heat capacity of the water should be pretty easy to get. What else is unknown? (One issue you may have in modelling is if there are convective heat currents in the water.) So what are your R's and C's?



George H.







Maybe I still will, out of interest, but it'll be a lot simpler to

interpolate from those measurements that I do have, and probably more

than adequate.







Sylvia.

That's very boring, like you're going to construct a homemade heater anywhere near as efficient as off-the-shelf models... but this is interesting, almost doubles the effective heat capacity of the tank, useful for people in situations of sporadic high demand:

http://www.cashacme.com/prod_thermostatics_WHTC_kit.php

 

On Friday, April 4, 2014 2:38:36 PM UTC-4, bloggs.fred...@gmail.com wrote:

http://www.cashacme.com/prod_thermostatics_WHTC_kit.php

Just noticed that jackass forgot to tell the other jackasses how to bleed the jackass tank before re-applying power...dammed jackasses.

 

[Jim Thompson]

On Fri, 04 Apr 2014 19:28:23 +1100, Clifford Heath
<no.spam@please.net> wrote:

On 04/04/14 15:04, Jim Thompson wrote:
On Fri, 04 Apr 2014 14:03:58 +1100, Clifford Heath
no.spam@please.net> wrote:
From my archives (and recently provided to Robert Macy for his noise
experiments)...
Some IC models (NPN) from that era...

Thanks, that second one is the same one I copied into the ASC file
below. is the CA3046_ORG the model originally from Intersil, and the
other is yours?

Yes.

My device is actually LM3046, but I don't expect any differences that
would affect things at 30MHz, though perhaps at 150.

Layouts are referenced in my other response.

Have you figured in the pin-to-pin capacitances of your package? DIL's
can run as high as 4pF.

Clifford Heath.

******************************************************************
.MODEL CA3046_ORG NPN IS=3.860200F BF=120 NF=1.04845 VAF=61.1026 IKF=
+ 50.000000M ISE=3.100000P NE=2.16533 BR=100.101000M NR=1.04845 ISC=0
+ NC=1 RB=214.644 RBM=214.644 RE=721.362980M RC=9.2065 CJE=1.249000P
+ VJE=899.999940M MJE=499.999970M TF=210.000000P XTF=1.85 VTF=1.585
+ ITF=50.000000M PTF=0 CJC=1.000000P VJC=749.999940M MJC=333.000000M
+ XCJC=499.999970M TR=10.000000N CJS=6.300000P VJS=749.999940M MJS=
+ 499.999970M XTB=1.5 EG=1.11 XTI=3 KF=0 AF=1 FC=499.999970M
*
*COPYRIGHT Š 1997 INTERSIL CORPORATION
*ALL RIGHTS RESERVED
*
*CA3046 PSpice MODEL
*REV: 2-24-97
** ----- BJT MODEL -----
*
.model CA3046 NPN
+ (IS = 10.0E-15 XTI= 3.000E+00 EG = 1.110E+00 VAF= 1.00E+02
+ VAR = 1.000E+02 BF = 145.7E+00 ISE = 114.286E-15 NE = 1.480E+00
+ IKF = 46.700E-03 XTB = 0.000E+00 BR = .1000E+00 ISC = 10.005E-15
+ NC = 2.000E+00 IKR = 10.00E-03 RC = 10.000E+00 CJC = 991.71E-15
+ MJC = 0.333E-00 VJC = 0.7500E-00 FC = 5.000E-01 CJE = 1.02E-12
+ MJE = .336E-00 VJE = 0.750E-00 TR = 10.000E-09 TF = 277.01E-12
+ ITF = 1.750E-00 XTF = 309.38E+00 VTF= 16.37E+00 PTF = 0.000E+00
+ RE = 0.0E+00 RB = 0.00E+00
*
*COPYRIGHT Š 1997 INTERSIL CORPORATION
*ALL RIGHTS RESERVED
*
*CA3086 PSpice MODEL
*REV: 2-24-97
** ----- BJT MODEL -----
*
.model CA3086 NPN
+ (IS = 10.0E-15 XTI= 3.000E+00 EG = 1.110E+00 VAF= 1.00E+02
+ VAR = 1.000E+02 BF = 156.6E+00 ISE = 114.886E-15 NE = 1.470E+00
+ IKF = 36.700E-03 XTB = 0.000E+00 BR = .1000E+00 ISC = 10.005E-15
+ NC = 2.000E+00 IKR = 10.00E-03 RC = 10.000E+00 CJC = 991.79E-15
+ MJC = 0.333E-00 VJC = 0.7500E-00 FC = 5.000E-01 CJE = 1.02E-12
+ MJE = .336E- 00 VJE = 0.750E-00 TR = 10.000E-09 TF = 278.55E-12
+ ITF = .770E-00 XTF = 91.38E+00 VTF= 18.37E+00 PTF = 0.000E+00
+ RE = 0.0E+00 RB = 0.00E+00
*
*COPYRIGHT Š 1997 INTERSIL CORPORATION
*ALL RIGHTS RESERVED
*
*CA3127 PSpice MODEL
*REV: 2-13-97
** ----- BJT MODEL -----
*
.model CA3127 NPN
+ (IS = 3.20p XTI= 3.000 EG = 1.110 VAF= 100
+ VAR = 100 BF = 95.2E ISE = 20.586p NE = 1.990
+ IKF = 61.500m XTB = 0 BR =100m ISC = 10.805n
+ NC = 2.000n IKR = 10m RC = 10m CJC = 281.1f
+ MJC = 0.138 VJC = 0.75 FC = 0.5 CJE = 651.9f
+ MJE = .336 VJE = 0.750 TR = 10n TF = 122.61p
+ ITF = 1.600p XTF = 2.050K VTF= 307 PTF = 0
+ RE = 0 RB = 0
* Application Note MM9701
******************************************************************
.SUBCKT CA3046PAK 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Q1 1 2 3 [SUB] CA3046
Q2 5 4 3 [SUB] CA3046
Q3 8 6 7 [SUB] CA3046
Q4 11 9 10 [SUB] CA3046
Q5 14 12 13 [SUB] CA3046
RSUB SUB 13 1
.ENDS CA3046PAK
******************************************************************

Folk,

Thanks to some good help here in the past, I have a nice clean
oscillator (for my new fox transmitters), but I'm having trouble with
the LTSpice simulation at higher frequencies. I'm assuming that the
Intersil Spice model for the CA3046 is bad, and I know JT has a better one.

Anyhow, I have two questions about the attached LTSpice schematic.

1) When I set it to 30MHz, LTSpice says the oscillator will start nicely
(even up to 150MHz in fact). Now I know that the (calculated) Colpitts
capacitance ratio is bad, as is the base capacitor, but with the
physical circuit built in a tight layout in SMD and a range of more
sensible capacitances substituted, I can't get it to oscillate above
about 12MHz. Why does it not want to run in real life, when Spice says
it should? Can someone provide me a better CA3046 model please, or say
what else might be going on?

2) I'd like some insight into the correct formulae to calculate the
Colpitts capacitive divider ratio, and the minimum safe base coupling
capacitor. The CA3046 data sheet says that Cbe and Ccb are both in the
range of 0.6pF, and the Ft is around 300MHz. So at 150MHz I only have
3dB of gain to play with, so that Cbe means I need at least a couple of
pF to drive the base, and the divider ratio has to give reasonable
drive. If anyone could suggest better "rule of thumb" for calculating
these things from Ft and Cin, I'd appreciate it.

Clifford Heath
-- Cut Here for OscProblem.asc --
Version 4
SHEET 1 2160 1200
WIRE 304 -336 192 -336
WIRE 752 -336 304 -336
WIRE 192 -288 192 -336
WIRE 192 -176 192 -208
WIRE 192 -176 -64 -176
WIRE 432 -176 192 -176
WIRE 528 -176 432 -176
WIRE 192 -128 192 -176
WIRE 752 -96 752 -336
WIRE 304 -48 304 -336
WIRE 432 -48 432 -176
WIRE -48 0 -64 0
WIRE 32 0 -48 0
WIRE 96 0 32 0
WIRE 192 0 192 -48
WIRE 192 0 160 0
WIRE 240 0 192 0
WIRE 32 64 32 0
WIRE 528 64 528 -176
WIRE -48 144 -48 0
WIRE 432 160 432 32
WIRE 32 208 32 128
WIRE 304 208 304 48
WIRE 304 208 32 208
WIRE 368 208 304 208
WIRE 192 256 192 0
WIRE 304 256 304 208
WIRE 32 272 32 208
WIRE -48 384 -48 224
WIRE 32 384 32 336
WIRE 32 384 -48 384
WIRE 192 384 192 336
WIRE 192 384 32 384
WIRE 304 384 304 336
WIRE 304 384 192 384
WIRE 432 384 432 256
WIRE 432 384 304 384
WIRE 528 384 528 128
WIRE 528 384 432 384
WIRE 752 384 752 -16
WIRE 752 384 528 384
WIRE 752 400 752 384
FLAG 752 400 0
FLAG -64 0 Vosc
IOPIN -64 0 Out
FLAG -64 -176 Vbias
IOPIN -64 -176 Out
SYMBOL voltage 752 -112 R0
WINDOW 123 24 126 Left 2
WINDOW 39 24 111 Left 2
SYMATTR InstName V1
SYMATTR Value 3.2v
SYMBOL cap 16 64 R0
SYMATTR InstName C1
SYMATTR Value {C1}
SYMBOL cap 16 272 R0
SYMATTR InstName C2
SYMATTR Value {C2}
SYMBOL ind -64 128 R0
SYMATTR InstName L3
SYMATTR Value {L1}
SYMBOL npn 240 -48 R0
SYMATTR InstName Q1
SYMATTR Value CA3046
SYMBOL res 176 -144 R0
SYMATTR InstName R4
SYMATTR Value 100k
SYMBOL npn 368 160 R0
SYMATTR InstName Q2
SYMATTR Value CA3046
SYMBOL res 176 -304 R0
SYMATTR InstName R2
SYMATTR Value 47k
SYMBOL cap 512 64 R0
SYMATTR InstName C4
SYMATTR Value {100/(F0*10k)}
SYMBOL res 288 240 R0
SYMATTR InstName R6
SYMATTR Value 2.2k
SYMBOL cap 160 -16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C3
SYMATTR Value {C3}
SYMBOL res 176 240 R0
SYMATTR InstName R3
SYMATTR Value 100k
SYMBOL res 416 -64 R0
SYMATTR InstName R8
SYMATTR Value 10k
TEXT 864 -424 Left 2 !.tran 0 {10u + (2000/F0)} 0 {1/(F0*50)}
TEXT -96 -384 Left 2 !.param F0=30Meg
TEXT -96 440 Left 2 !; Calculate main tank components from F0, ZT and
stray capacitances:\n.param CSTRAY1=1.7p CSTRAY2=0.8pF\n.param
L1={ZT/(2*PI*F0)} DIV=17 C2={1/(2*PI*F0*(ZT/DIV)) - CSTRAY1}
CT={(1/(2*PI*F0*ZT)) - CSTRAY2} C1={1/((1/CT) - (1/C2))}\n.MEASURE L1_
PARAM L1\n.MEASURE C1_ PARAM C1\n.MEASURE C2_ PARAM C2
TEXT 872 232 Left 2 !.param ZCouple1=5k C3={max(1/(2*PI*F0*ZCouple1),
1pF)}\n.MEASURE C3_ PARAM C3
TEXT -96 -344 Left 2 !.param ZT=350
TEXT 872 144 Left 2 !.MEASURE C4_ PARAM {100/(F0*10k)}
TEXT 864 -320 Left 2 !*COPYRIGHT Š 1997 INTERSIL CORPORATION\n*ALL
RIGHTS RESERVED\n*\n*CA3046 PSpice MODEL\n*REV: 2-24-97\n** ----- BJT
MODEL -----\n*\n.model CA3046 NPN\n+ (IS = 10.0E-15 XTI=3.000E+00
EG=1.110E+00 VAF=1.00E+02\n+ VAR=1.000E+02 BF=145.7E+00 ISE=114.286E-15
NE=1.480E+00\n+ IKF=46.700E-03 XTB=0.000E+00 BR=.1000E+00
ISC=10.005E-15\n+ NC=2.000E+00 IKR=10.00E-03 RC=10.000E+00
CJC=991.71E-15\n+ MJC=0.333E-00 VJC=0.7500E-00 FC=5.000E-01
CJE=1.02E-12\n+ MJE=.336E-00 VJE=0.750E-00 TR=10.000E-09
TF=277.01E-12\n+ ITF=1.750E-00 XTF=309.38E+00 VTF=16.37E+00
PTF=0.000E+00\n+ RE=0.0E+00 RB=0.00E+00
TEXT -96 -424 Left 2 ;Change these parameters to vary the operating
frequency and tank impedance
TEXT 696 560 Left 2 ;This model was initially designed and built (works
fine) at 3.58 MHz.\nWhen run at any frequency up to 150MHz, it still
simulates fine.\nHowever, the physical circuit only reaches half
amplitude at 12MHz,\nand doesn't start at all much above that, even when
larger C3 and\nsmaller C1/C2 ratio is used (to overcome lower gain,
input capacitance;\n1pf for C3 cannot ever be enough with Cbe=0.5pF
Ft=300MHz).\nI'd really like to know why. Is my CA3046 model wrong?

...Jim Thompson

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

[Jim Thompson]

On Fri, 4 Apr 2014 00:47:25 -0700 (PDT), gyansorova@gmail.com wrote:

On Thursday, April 3, 2014 7:09:31 PM UTC+13, Jim Thompson wrote:
On Wed, 2 Apr 2014 22:51:51 -0700 (PDT), gyansorova@gmail.com wrote:



On Wednesday, April 2, 2014 5:40:31 PM UTC+13, Sylvia Else wrote:

I have the circuit whose LTSPICE text is given below. The voltage



sources and voltage controlled switches are only there to set the



initial voltages on the capacitors. Thus the circuit of interest



consists of two capacitors and two resistors.







I've been trying to determine an equation that describes the voltage on



C2 as it varies with time, but with my limited mathematical skill,



haven't been able to. I end up with differential equations that contain



the voltage on C1 as well, in a way that I can't substitute for.







Any thoughts?







Sylvia.





First of all can we see a circuit diagram instead of a Spice listing!!!

Secondly what voltage is the input ie dc a sine wave etc



Sylvia posted an LTspice .ASC file, which _is_ a schematic.



...Jim Thompson

--

| James E.Thompson | mens |

| Analog Innovations | et |

| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |

| San Tan Valley, AZ 85142 Skype: Contacts Only | |

| Voice480)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.

Well all I see is a list of numbers! I need a real circuit diagram.

Advice to smart-ass little wimp fuck-head... get with the action and
install LTspice.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

[RobertMacy]

On Fri, 04 Apr 2014 01:28:23 -0700, Clifford Heath <no.spam@please.net>
wrote:

>> ...snip, way too much ....

Alex Bordordunov [incredibly prolific producer of effective models and
able electronic designer!] just sent me this model:

"Hi Robert,
I have found the more neat (exact) model a model transistor CA3046.
.MODEL CA3046 NPN(IS=10f BF=145.76 VAF=100 IKF=46.747m ISE=114.23f
NE=1.483 BR=100.1m VAR=100 IKR=10.01m ISC=10f RC=10 CJE=1.026p MJE=333.33m
CJC=991.79f MJC=333.33m TF=277.09p XTF=309.38 VTF=16.364 ITF=1.7597
TR=10n CJS=6.3P VJS=0.749 MJS=0.5 VCEO=20 ICRATING=50m MFG=RCA)
To LTspice used the additional parameters to models (CJS, VJS, MJS)
necessary to use the symbol NPN4.

Alex."


He has over 35MB of models, which he posted to the LTspice group.

I am trying to put the two of you in contact. send me your email address.
Meanwhile, try his model and let us know if it acts much differently.

Don't be offended, ...wrap the lines properly.

 

[RobertMacy]

On Fri, 04 Apr 2014 08:38:50 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

...snip....

Have you figured in the pin-to-pin capacitances of your package? DIL's
can run as high as 4pF.

4 pf ?!!! 400 ohms at 100MHz!! Words of, "Don't even THINK about trying
to get impedances above free space." echo in my ears.

should we also add the tiny 'common mode' transformer action inside those
leads, too? After all, they are parallel conductors too, right?

 

[Mike Perkins]

On 04/04/2014 08:47, gyansorova@gmail.com wrote:

On Thursday, April 3, 2014 7:09:31 PM UTC+13, Jim Thompson wrote:
On Wed, 2 Apr 2014 22:51:51 -0700 (PDT), gyansorova@gmail.com wrote:



On Wednesday, April 2, 2014 5:40:31 PM UTC+13, Sylvia Else wrote:

I have the circuit whose LTSPICE text is given below. The voltage



sources and voltage controlled switches are only there to set the



initial voltages on the capacitors. Thus the circuit of interest



consists of two capacitors and two resistors.







I've been trying to determine an equation that describes the voltage on



C2 as it varies with time, but with my limited mathematical skill,



haven't been able to. I end up with differential equations that contain



the voltage on C1 as well, in a way that I can't substitute for.







Any thoughts?







Sylvia.





First of all can we see a circuit diagram instead of a Spice listing!!!

Secondly what voltage is the input ie dc a sine wave etc



Sylvia posted an LTspice .ASC file, which _is_ a schematic.



...Jim Thompson

--

| James E.Thompson | mens |

| Analog Innovations | et |

| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |

| San Tan Valley, AZ 85142 Skype: Contacts Only | |

| Voice480)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.

Well all I see is a list of numbers! I need a real circuit diagram.

It's easy to install LTspice, which is free, and cut and past the list
of numbers into a file and open it with LTspice.

This group can only have text so no schematics.

--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk

 

[Clifford Heath]

On 05/04/14 02:38, Jim Thompson wrote:

Have you figured in the pin-to-pin capacitances of your package? DIL's
can run as high as 4pF.

No - but it's an SSOP. Pin capacitances? No idea.

 

[Clifford Heath]

On 05/04/14 00:41, Tauno Voipio wrote:

On 4.4.14 11:44, Clifford Heath wrote:

But first, I'd like a better guess (or I know, math...) at plausible
values for these parts to make it oscillate at 30MHz, before I try 50 or
150.

You are running the transistor at a very low current.

Ahh, good point. I'll run it a little hotter.
Battery power, but a couple more mA won't hurt.

It may be limiting its capability of handling the
strays from the ground plane at higher frequencies.

Out of curiosity, I dropped the resistances by a factor
of 10, and the thing at least simulates well.

Another vote to dropping the R and C from the top
of the varactor chain. Also, another vote to taking
the output from the emitter.

 

[Jim Thompson]

On Sat, 05 Apr 2014 07:37:05 +1100, Clifford Heath
<no.spam@please.net> wrote:

On 05/04/14 02:38, Jim Thompson wrote:
[snip]
Have you figured in the pin-to-pin capacitances of your package? DIL's
can run as high as 4pF.

No - but it's an SSOP. Pin capacitances? No idea.

Some of those package are as low as 0.15 to 0.2pF between pins. Add
pin-to-pin capacitance to your model as a parameter and play with it
to see what matters.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

[Clifford Heath]

On 05/04/14 00:25, Chris Jones wrote:

On 04/04/2014 19:44, Clifford Heath wrote:
[snip]
any photos? of the circuitry? Don't wish to cast aspersions, but layout
above 10 MHz starts to become important. up there a short connection is
no longer a connection,

Yes, I'm aware of that. I've routed it single-sided on a copper rear
plane, using 0805 components throughout. Within that constraint, I'll be
very surprised if you can find a way to substantially improve it... but
here are the snapshots of this part of the circuit (from Eagle):
http://cjh.polyplex.org/electronics/fox/Oscillator.brd.png
http://cjh.polyplex.org/electronics/fox/Oscillator.sch.png
[snip]

Thanks for posting the diagrams.

Some loss in the inductor would certainly be more realistic. I hope the
inductor is not sitting right on the PCB unless you make a big hole in
the ground plane under the inductor, at least 2x the diameter of the
inductor.

I wasn't aware that much flux will escape the toroid? I'm sure I've seen
this done successfully elsewhere. In any case in my prototype the toroid
is floating on 2cm leads, so could flop into different places (this is
the low-HF version that works fine) and at VHF I have an air coil
mounted a few mm above the board.

Otherwise it is going to reduce the Q like a shorted turn. As

long the hole is big enough so that the ground plane is spaced far
enough from the turns, it is no longer a problem and actually helps with
shielding the inductor.

I note that you are taking the output via C9 from the top of the tank,
which is a very sensitive node. I hope it is going to something with
really low loss, or that could be a cause for reducing the Q and
tendency to oscillate. I would suggest taking the output from some
low-impedance node, such as a tap on the inductor, or the top of R6 or
something like that.

I have a very small coupling cap to a BJT buffer/phase-splitter node
with pretty high impedance. The simulator shows the tank tap is cleaner
than the signal at the emitter, and I was trying to keep things pure and
linear as possible to avoid later filtering (note it's a VCO). I'll keep
that in mind at higher frequencies though, perhaps switch to a JFET
buffer/splitter.

Also not related to the present problem, I think you could probably get
rid of C6 and R7 - the DC voltage on each side of C6 is the same,
assuming the varactors stay reverse biased.

Ahh, good point. I cargo-culted that from a circuit where the tank was hot.

Thanks for your thoughts.

Clifford Heath.

 

[Clifford Heath]

On 05/04/14 02:45, RobertMacy wrote:

On Fri, 04 Apr 2014 01:28:23 -0700, Clifford Heath <no.spam@please.net
wrote:

...snip, way too much ....

Alex Bordordunov [incredibly prolific producer of effective models and
able electronic designer!] just sent me this model:

Fantastic, I'll try it later today.

"Hi Robert,
I have found the more neat (exact) model a model transistor CA3046.
.MODEL CA3046 NPN(IS=10f BF=145.76 VAF=100 IKF=46.747m ISE=114.23f
NE=1.483 BR=100.1m VAR=100 IKR=10.01m ISC=10f RC=10 CJE=1.026p
MJE=333.33m CJC=991.79f MJC=333.33m TF=277.09p XTF=309.38 VTF=16.364
ITF=1.7597 TR=10n CJS=6.3P VJS=0.749 MJS=0.5 VCEO=20 ICRATING=50m MFG=RCA)
To LTspice used the additional parameters to models (CJS, VJS, MJS)
necessary to use the symbol NPN4.

Alex."
He has over 35MB of models, which he posted to the LTspice group.
I am trying to put the two of you in contact. send me your email
address.

firstname.lastnmae@gmail.com

Meanwhile, try his model and let us know if it acts much
differently.

Thanks, I will do.

> Don't be offended, ...wrap the lines properly.

Do you mean "let the reader wrap the lines"? Yes, ok, a lot of people
read on displays narrower than 80 columns now. Really? I have a 40-year
habit of wrapping text, which I'm trying to break... bear with me

Clifford Heath.

 

[Clifford Heath]

On 04/04/14 22:49, Chris Jones wrote:

On 04/04/2014 14:03, Clifford Heath wrote:
Thanks to some good help here in the past, I have a nice clean
oscillator (for my new fox transmitters), but I'm having trouble with
the LTSpice simulation at higher frequencies. I'm assuming that the
Intersil Spice model for the CA3046 is bad, and I know JT has a better
one.

Anyhow, I have two questions about the attached LTSpice schematic.

1) When I set it to 30MHz, LTSpice says the oscillator will start nicely
(even up to 150MHz in fact). Now I know that the (calculated) Colpitts
capacitance ratio is bad, as is the base capacitor, but with the
physical circuit built in a tight layout in SMD and a range of more
sensible capacitances substituted, I can't get it to oscillate above
about 12MHz. Why does it not want to run in real life, when Spice says
it should? Can someone provide me a better CA3046 model please, or say
what else might be going on?
[snip]
I would suggest estimating the length of some of the more critical
physical wires on the hardware version, and putting appropriate
parasitics back into the simulation model. Particularly in series with
the emitter of transistors, it can affect gain at RF. I would suggest
modelling the emitter pin and leadframe and the wiring as 1nH per
millimetre of length, as a first guess, plus another nanohenry for the
bondwire (unless it is already in your transistor model). Whilst this
probably isn't the cause, it might start to expain something.

The whole oscillator fits in 1cmx2cm - leads are really short. I'd be
surprised if parasitics are a problem as low as 30MHz. Fair enough to
worry at UHF, but even at 150MHz I don't think my layout is bad. I need
find out though!

I think I could pretty easily switch to discretes (say MMBT2222A) which
have a similar-ish Ft etc, and that could improve the layout a little.
Especially by getting pin 8 (collector of the phase-splitter) away from
the oscillator device.

Another thing that may be worth trying, though it isn't usually
necessary until you get to GHz frequencies: The capacitance across
unwanted junctions on chips (perhaps collector to substrate in your
case) can be lossy.

What sort of capacitance would I expect between two SSOP pins?

and for a 10mil trace, what capacitance through ordinary 1.6mm FR4?

If you model it as a pure capacitor then you can

simulate better Q or gain or noise figure than reality. Of course if you
add an infinite value resistor in series with the parasitic capacitances
then that also gives zero losses and artificially good performance.
There is some intermediate value of resistance to put in the model in
series with the parasitic capacitance, between zero and infinity Ohms,
that will result in the worst possible losses. There is some other value
of series resistance that is the best model of reality. Often the most
representative value is close to the worst case losses value, except
when you don't want things to oscillate in which case it is very different.

It is important to put some losses in the model of your inductor also,
as another poster mentioned. Beware of metal very close to the inductor.
I sometimes like to put inductors in screened cans, but all metalwork
should ideally be spaced away from the turns of the inductor by at least
the inductor diameter, to avoid causing more losses.

I planned to box the whole oscillator, but it's hard to develop that way .

Hopefully you have some low-ESR decoupling (e.g. 100n chip ceramic)
capacitor(s) across your supply right near the oscillator. Otherwise the
impedance of the supply wiring might stop things from working, in a way
that would not be simulated.

Yes, the collector of both oscillator and AGC transistor have 0805 caps
directly to a ground via.

I'm using caps from a cheap Chinese SMD book... I hope they're ok.

I suggest you get one of those label machines, and affix a label to your
prototype that says "unconditionally stable amplifier". It will surely
oscillate then.

Are you able to verify the DC collector current and Vce of your
not-oscillating transistor? I would check that the collector current is
close to (but slightly lower than) the value that gives the peak Ft
value.

I don't even know what current that is. Will check the data sheet.

(I have been warned that above the current that gives peak Ft,
models are often not very good and/or device performance is more
unpredictable, and to therefore stay somewhat below that current if good
Ft is important). Also make sure the Vce is well over a volt,

Ahhh, ok, it's just over a volt - about 1.7v I think. Supply is only 3.2V.

and more

if the transistor has a poorly contacted collector with lots of
distributed resistance (which could cause parts of the device to
saturate before other parts, and wouldn't usually be modelled).

For oscillators, I like to pick a transistor with an Ft that is about 10
times higher than the highest desired oscillation frequency. Something
like an old BFY90, in your case, or one of the many surface mount RF
transistors that you can get these days.

Thought I had some BFR93A's here and wanted to splice one in to the
existing layout (cut pins and hot-wire the SOT23 on top of the LM3046),
but I can't find them. Maybe too fast, but still...

Actually I prefer FET LC
oscillators but none of this is really relevant to the simulation problem.

Well, I'll experiment with BF862's for VHF work. Not sure how well that
will go with a 3.2V supply (Vgs is a bit unpredictable). This existing
design is useful even if I can't get it to run at VHF, but I really want
to learn what I've done wrong anyhow.

--
Clifford Heath

 

[Jim Thompson]

On Fri, 04 Apr 2014 14:03:58 +1100, Clifford Heath
<no.spam@please.net> wrote:

[snip]

You apparently have multiple line-wrap issues in your .asc file.

Try not putting everything in one line ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

[Clifford Heath]

On 05/04/14 11:49, RobertMacy wrote:

On Fri, 04 Apr 2014 13:58:46 -0700, Clifford Heath <no.spam@please.net
wrote:
...snip...
Thanks, I will do.
...snip...
I just tested it in a sample circuit, that new model is 1/3 the speed of
the other model!
Envision grounded base with current source(s) to emitter. collector has
1k load with about 5mA bias current.
Also substrate voltage at -8Vdc.

Roll off of old model approx 190MHz, new model 64.5MHz! significant
differences there.

Wow, yes, big difference. However the Ft of the CA3046 is meant to be
around 300MHz, whereas the LM3046 is min 300, typical 550. I don't
really know how much gain your test circuit was asking for, but they do
say "DC to 120MHz" on the National data sheet... Maybe I'm asking too
much to push to 150MHz, but surely not to 30?

That said, I was just playing with parallel R loading the tank, and it
doesn't take much to drop the amplitude way down... it seems likely that
my original problem was excessive tank loading.

> Plus has a bit more noise, if that's important.

Make it a bit more likely to start perhaps

--
Clifford Heath

 

[Jim Thompson]

On Fri, 4 Apr 2014 22:11:54 -0700 (PDT), gyansorova@gmail.com wrote:

[delete gmail multi-spaced]

>There is help for your autism - you do realise that do you not?

Crikey, another schmuck in the image of Phil Allison. You're history.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

[Jim Thompson]

On Fri, 4 Apr 2014 22:11:12 -0700 (PDT), gyansorova@gmail.com wrote:

[snip]

Never heard of tinypic and such web sites? I don't use spice I have Multisim if I need to do such things. Maybe I can use it but it would be far easier just to post the pic to tinypic.

Do you think you are special? You're not. You're "common" in the
most base definition of that word.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)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.

 

On Sunday, April 6, 2014 3:31:50 AM UTC+12, Jim Thompson wrote:

On Fri, 4 Apr 2014 22:11:12 -0700 (PDT), gyansorova@gmail.com wrote:



[snip]



Never heard of tinypic and such web sites? I don't use spice I have Multisim if I need to do such things. Maybe I can use it but it would be far easier just to post the pic to tinypic.



Do you think you are special? You're not. You're "common" in the

most base definition of that word.



...Jim Thompson

--

| James E.Thompson | mens |

| Analog Innovations | et |

| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |

| San Tan Valley, AZ 85142 Skype: Contacts Only | |

| Voice480)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.

You are clearly autistic, nothing else. Get help.

 

[Maynard A. Philbrook Jr.]

In article <mb60k9hkehfvs9nqjpg7lk9at3bonhfmpu@4ax.com>, To-Email-Use-
The-Envelope-Icon@On-My-Web-Site.com says...

On Fri, 4 Apr 2014 22:11:54 -0700 (PDT), gyansorova@gmail.com wrote:

[delete gmail multi-spaced]

There is help for your autism - you do realise that do you not?

Crikey, another schmuck in the image of Phil Allison. You're history.

...Jim Thompson

That list must be getting long by now.

Jamie

 

On Saturday, April 5, 2014 12:16:04 AM UTC-4, Sylvia Else wrote:

On 5/04/2014 5:38 AM, bloggs.fredbloggs.fred@gmail.com wrote:



That's very boring, like you're going to construct a homemade heater

anywhere near as efficient as off-the-shelf models



Who mentioned efficiency? I certainly didn't.



Sylvia.

Yes, of course, that would have been to practical for someone like you. Looks like you're hung up on much more elementary considerations.