Tech 167...

SgtWookie

Joined Jul 17, 2007
22,230
Just adding to Thingmaker's comment,
The 7493 is a 4-bit binary up-counter.
If you're going to use an R2R ladder on the outputs to create a ramp generator, I suggest that you use the 74HC93.
Whether the ramp slopes up or slopes down depends upon how you connect the R2R ladder to the outputs of the '93 counter.

See the attached for a similar idea.

The LF351 is used as a buffer amplifier. It was really not a good choice for this application, because the inputs and outputs are not rail to rail, but it works OK for the first 14 of the 16 discrete steps. Since CMOS logic has very limited output current, the R2R values need to be rather high; so a buffer amplifier is necessary for all but very high impedance outputs.

The LM339 provides a means to terminate the ramp early, by resetting the counter.
The 4020 is a CMOS dual binary up-counter.
 

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Thread Starter

Rajit28

Joined Oct 21, 2008
49
Just adding to Thingmaker's comment,
The 7493 is a 4-bit binary up-counter.
If you're going to use an R2R ladder on the outputs to create a ramp generator, I suggest that you use the 74HC93.
Whether the ramp slopes up or slopes down depends upon how you connect the R2R ladder to the outputs of the '93 counter.

See the attached for a similar idea.

The LF351 is used as a buffer amplifier. It was really not a good choice for this application, because the inputs and outputs are not rail to rail, but it works OK for the first 14 of the 16 discrete steps. Since CMOS logic has very limited output current, the R2R values need to be rather high; so a buffer amplifier is necessary for all but very high impedance outputs.

The LM339 provides a means to terminate the ramp early, by resetting the counter.
The 4020 is a CMOS dual binary up-counter.
any recommendations for buffer amplifiers welcome.
 

Thread Starter

Rajit28

Joined Oct 21, 2008
49
Best place to find clocks for 7493 IC chips.

the clock measures pulse length in micro seconds i think

not sure.:)
 

beenthere

Joined Apr 20, 2004
15,819
Do you need a clock source? You can find clock oscillators with logic outputs in 4 pin IC packages. A 1 MHz oscillator will give microsecond timing.
 

Thread Starter

Rajit28

Joined Oct 21, 2008
49
Do you need a clock source? You can find clock oscillators with logic outputs in 4 pin IC packages. A 1 MHz oscillator will give microsecond timing.
do you know where to get 4 pin IC packages. in my college we normally

use 16 pins or 8 pins or something 4 pins looks a little small

don't you think?:confused:
 
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