1.6v to 5v

J

Jamie Morken

Jan 1, 1970
0
Hi all,

I have a 1.6V volt squarewave (output of an RF prescaler) that I would like
to use to drive the clock of a binary counter chip (I am trying to make an
RF frequency counter) The 1.6V signal has a MAX frequency of 50MHz. I need
to convery the 1.6V signal into a 5V squarewave to drive the counters clock
input. The circuit that I am using as a guide
(http://www.aade.com/dfd4.htm) uses a 4046 PLL chip between the RF prescaler
and the counter chip, but I am not sure how this works. Would using a high
speed opamp work for this? The counter chip I am using is the 74VHC393 Dual
4-bit binary counter. Thanks for your time,

cheers,
Jamie Morken

A

Al Borowski

Jan 1, 1970
0
Jamie said:
Hi all,

I have a 1.6V volt squarewave (output of an RF prescaler) that I would like
to use to drive the clock of a binary counter chip (I am trying to make an
RF frequency counter) The 1.6V signal has a MAX frequency of 50MHz. I need
to convery the 1.6V signal into a 5V squarewave to drive the counters clock
input.

Maybe I'm being naive at 50MHz, but surely you could just use a BJT?

+5V
|
.-.
| |
| |
'-'
| Out
-----------
|
___ |/
---------|___|------|
In |>
|
|
===
GND

created by Andy´s ASCII-Circuit v1.22.310103 Beta www.tech-chat.de

Al

F

Fred Bloggs

Jan 1, 1970
0
Jamie said:
Hi all,

I have a 1.6V volt squarewave (output of an RF prescaler) that I would like
to use to drive the clock of a binary counter chip (I am trying to make an
RF frequency counter) The 1.6V signal has a MAX frequency of 50MHz. I need
to convery the 1.6V signal into a 5V squarewave to drive the counters clock
input. The circuit that I am using as a guide
(http://www.aade.com/dfd4.htm) uses a 4046 PLL chip between the RF prescaler
and the counter chip, but I am not sure how this works. Would using a high
speed opamp work for this? The counter chip I am using is the 74VHC393 Dual
4-bit binary counter. Thanks for your time,

cheers,
Jamie Morken

This is best handled by a high speed single-supply comparator with CMOS
compatible output- see:
http://para.maxim-ic.com/compare.asp?Fam=Comp&Tree=Comparators&HP=AmpComp.cfm&ln=

J

John Larkin

Jan 1, 1970
0
Hi all,

I have a 1.6V volt squarewave (output of an RF prescaler) that I would like
to use to drive the clock of a binary counter chip (I am trying to make an
RF frequency counter) The 1.6V signal has a MAX frequency of 50MHz. I need
to convery the 1.6V signal into a 5V squarewave to drive the counters clock
input. The circuit that I am using as a guide
(http://www.aade.com/dfd4.htm) uses a 4046 PLL chip between the RF prescaler
and the counter chip, but I am not sure how this works. Would using a high
speed opamp work for this? The counter chip I am using is the 74VHC393 Dual
4-bit binary counter. Thanks for your time,

cheers,
Jamie Morken

Run the signal into the input of a fast cmos logic gate - say an HC04
or an AC04 - and add a dc feedback resistor, 100k maybe, from the gate
output back to its input. It will then self-bias at a nice operating
point, and amplify your input nicely.

John

J

Jan 1, 1970
0
B

budgie

Jan 1, 1970
0
Hi all,

I have a 1.6V volt squarewave (output of an RF prescaler) that I would like
to use to drive the clock of a binary counter chip (I am trying to make an
RF frequency counter) The 1.6V signal has a MAX frequency of 50MHz. I need
to convery the 1.6V signal into a 5V squarewave to drive the counters clock
input. The circuit that I am using as a guide
(http://www.aade.com/dfd4.htm) uses a 4046 PLL chip between the RF prescaler
and the counter chip, but I am not sure how this works. Would using a high
speed opamp work for this? The counter chip I am using is the 74VHC393 Dual
4-bit binary counter. Thanks for your time,

I'm with Big Al on this - a simple junction transistor. If it's good enough for
us to use them as the squaring amps in the RF front-end of our 500MHz counters,
it is surely more than adequate at 50MHz. And also the cheapest solution, both
in $and solder joints. F Fred Bloggs Jan 1, 1970 0 budgie said: I'm with Big Al on this - a simple junction transistor. If it's good enough for us to use them as the squaring amps in the RF front-end of our 500MHz counters, it is surely more than adequate at 50MHz. And also the cheapest solution, both in$ and solder joints.

Ahhh- how right you are!!! Those damned dumb semi-manu's investing
millions per year in comparator product development, production, and
support- when all this time they can be replaced by a single
transistor... sure am glad to read to S.E.D. and get the inside track on
that rip-off from the whiz-bang pros...

B

budgie

Jan 1, 1970
0
Ahhh- how right you are!!! Those damned dumb semi-manu's investing
millions per year in comparator product development, production, and
support- when all this time they can be replaced by a single
transistor... sure am glad to read to S.E.D. and get the inside track on
that rip-off from the whiz-bang pros...

Do I detect a touch of sarcasm?

W

Winfield Hill

Jan 1, 1970
0
John Larkin wrote...
Run the signal into the input of a fast cmos logic gate - say an HC04
or an AC04 - and add a dc feedback resistor, 100k maybe, from the gate
output back to its input. It will then self-bias at a nice operating
point, and amplify your input nicely.

| ,---/\/\---,
| | |\ |
| ----||---+---| >O---+----
| |/

Jamie, this is your best solution. John's auggesting an ac-coupled
cmos amplifier made from an inverter. Simple, only two parts with
a spare 5V inverter, and it works well. I've used this trick at the
1.2V level: thousands in production over a 10-year period without a
hitch. Recommended whenever a continuous square-wave source is present.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

F

Fred Bloggs

Jan 1, 1970
0
Winfield said:
John Larkin wrote...

| ,---/\/\---,
| | |\ |
| ----||---+---| >O---+----
| |/

Jamie, this is your best solution. John's auggesting an ac-coupled
cmos amplifier made from an inverter. Simple, only two parts with
a spare 5V inverter, and it works well. I've used this trick at the
1.2V level: thousands in production over a 10-year period without a
hitch. Recommended whenever a continuous square-wave source is present.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

I know you do- a junior engineer at work used a similar junk circuit
from your book ( without comprehension- probably like most of your
readers) in a reference clock chain- I made him take it out- eliminated
ridiculous phase noise problems.

J

Jim Thompson

Jan 1, 1970
0
I know you do- a junior engineer at work used a similar junk circuit
from your book ( without comprehension- probably like most of your
readers) in a reference clock chain- I made him take it out- eliminated
ridiculous phase noise problems.

It works well with a 74HCU04
^---- NOTE the "U"

But with a 74HC04 (NO "U") it'll do bizarre things on its own.

I use it occasionally in custom ASICs, to get from PECL square waves
to CMOS, but the first inverter is **tiny**, otherwise you can get
substantial rail-to-rail current.

...Jim Thompson

H

Hal Murray

Jan 1, 1970
0
| ,---/\/\---,
I know you do- a junior engineer at work used a similar junk circuit
from your book ( without comprehension- probably like most of your
readers) in a reference clock chain- I made him take it out- eliminated
ridiculous phase noise problems.

Where is the phase noise coming from?

K

Ken Smith

Jan 1, 1970
0
Where is the phase noise coming from?

The input of a CMOS logic gate has a largish noise voltage. The exact
timing of the output's edge is determined by when the sum of this noise
voltage and the input signal crosses through the transition point.

Internally, most CMOS inverters look like 3 simple inverters in a
row. Think of the first stage as a voltage controlled current source
charging a capacitor. The slope of the ramp generated, depends on the
current and the capacitance. With less voltage swing on the input, there
is less current and hence a slower slope. The slower internal slope
allows the second stage's input noise to be a bigger factor.

If the CMOS chip has other signals on it, it can happen that the internal
capacitances cause timing interactions. This is commonly seen in such
things as divider chains. If you take the Q1 output of a divider chip you
will often see its timing vary depending on what Q2...Qn are doing at that
same instant.

H

Hul Tytus

Jan 1, 1970
0
An hc04u version (unbuffered) won't oscillate on it's own.

Hul

H

Hul Tytus

Jan 1, 1970
0
And ---- couple the input to the hc04(u) capacitively.

Hul