A
Amanda Robin
- Jan 1, 1970
- 0
I am breadboarding an amplifier/LP filter circuit using an INA125
instrumentation amp, ECS 1 MHz clock to generate signal for the filter
cutoff, a NAND gate to boost the clock output (thanks to Don Bruder for
explaining this in an earlier post), and a Maxim 281 Bessel LP filter.
The amp is powered at +- 15 V (using the breadboard's power supply), and
I am using LM7805 and 7905 voltage regulators to provide +- 5 V for the
rest of the chips.
I breadboarded the amp, clock, and NAND gate successfully, with all
components working properly. The trouble started after I added the Maxim
chip.
At this point I have checked and rechecked my connections, but the
following two problems remain: 1) the output of the NAND is saturated at
+5 V rather than generating a square wave, and 2) the output of the
Maxim filter is malformed. It is sinusoidal (like what I'm putting in)
but it flatlines every time it crosses ground. The LP filter is working,
however, with the right cutoff set.
Like this, but with curvature to the sinusoidal part. (12 point Courier)
*
* *
* *
**** **** ****
* *
* *
*
It does this with other waveforms, too.
I can input the clock signal directly into the LP filter, skipping the
NAND, and the right cutoff is still set, but the output is still
malformed. (Maybe I don't need the NAND, but since I'm eventually going
to serve several circuits with the same clock, I'll keep it for now.)
I have separated my analog and digital grounds (connected in one place
only). Another thought I had was that since I am using a quad NAND gate,
do I need to do anything to the other three gates? There are only 4 pin
connections currently: 1A (input), 1B (grounded), 1Y (output), and
ground.
I feel like it's an analog/digital problem, but I don't know how to
isolate it since I have to have the clock chip running to use the Maxim.
The thing I can think of to do next is to take the Maxim and its
connections off the board to see if the NAND output corrects, and make
sure it didn't get damaged by something I may have done. I don't want to
just switch in another one in case my board is currently a Toxic NAND
Gate Killer.
Also I suspect the voltage regulators, but they do seem to be
functioning correctly.
I would be very grateful for any help.
Amanda
instrumentation amp, ECS 1 MHz clock to generate signal for the filter
cutoff, a NAND gate to boost the clock output (thanks to Don Bruder for
explaining this in an earlier post), and a Maxim 281 Bessel LP filter.
The amp is powered at +- 15 V (using the breadboard's power supply), and
I am using LM7805 and 7905 voltage regulators to provide +- 5 V for the
rest of the chips.
I breadboarded the amp, clock, and NAND gate successfully, with all
components working properly. The trouble started after I added the Maxim
chip.
At this point I have checked and rechecked my connections, but the
following two problems remain: 1) the output of the NAND is saturated at
+5 V rather than generating a square wave, and 2) the output of the
Maxim filter is malformed. It is sinusoidal (like what I'm putting in)
but it flatlines every time it crosses ground. The LP filter is working,
however, with the right cutoff set.
Like this, but with curvature to the sinusoidal part. (12 point Courier)
*
* *
* *
**** **** ****
* *
* *
*
It does this with other waveforms, too.
I can input the clock signal directly into the LP filter, skipping the
NAND, and the right cutoff is still set, but the output is still
malformed. (Maybe I don't need the NAND, but since I'm eventually going
to serve several circuits with the same clock, I'll keep it for now.)
I have separated my analog and digital grounds (connected in one place
only). Another thought I had was that since I am using a quad NAND gate,
do I need to do anything to the other three gates? There are only 4 pin
connections currently: 1A (input), 1B (grounded), 1Y (output), and
ground.
I feel like it's an analog/digital problem, but I don't know how to
isolate it since I have to have the clock chip running to use the Maxim.
The thing I can think of to do next is to take the Maxim and its
connections off the board to see if the NAND output corrects, and make
sure it didn't get damaged by something I may have done. I don't want to
just switch in another one in case my board is currently a Toxic NAND
Gate Killer.
Also I suspect the voltage regulators, but they do seem to be
functioning correctly.
I would be very grateful for any help.
Amanda
