SUPPLEMENTAL LM13700 APPLICATION
At the time
when the LM13600/LM13700 datasheet was done, management
was beginning to feel that the number of applications was getting out
The LM13600/LM13700 data sheet was attempting to follow the LM3900 data
sheet in that it now allowed customers to do things which up until then
not convenient. This application supplement attempts to add a few more
as to how this Operational Transconductive Amplifier can be used.
IC was some what done at the request of an Analog Organ manufacturer.
Actually it was done as training lay out for a new mask designer. Some
managed to get turned into an actual IC, which was very unusual.
not keen on supporting the creation of a new IC for a yet to be created
course the first application was as a Voltage Controlled
Amplifier. The Organ
people needed to be be able to adjust the attack and decay of a tone,
spice today that can be simulated mathematically.
The whole Operational Transconductance Amplifier can be defined in one
0 I = -1*v(VIABC)*tanh((v(INP)-v(INN))/.052)
RL = 100
^ _/\ /\ /\__
/_\ | \/ \/
___ |\ _| _
VIN ____ |INP|__|+\/ \/
\ _|_ ___ |\ ___
_|_ |___| | / /\ \_|OUT|__|INB|_|
\ ___ | \ \/ / |___|
|___| | / |___|
// \ \ |INN|__|-/\_/\_/
\___/ _|_ B_OTA1
a PWL source (VIABC) is set to
track IABC over time...
( 0m 0m
10m 0m )
is an extra feature in that the definition of the buffer need not
0 V = v(OUT)
0 V = v(OUT) -1.2V
can make the spice netlist of attack and
decay simulations extremely simple.
data sheet lists a voltage control lowpass
filter as a typical application because of
a home Hi Fi project. The idea was to adjust the bandwidth of the audio
to always match the bandwidth of the music. A noticeable reduction in
cassette tapes was the result. The Home project work so well that Delco
to use it instead of Dolby. More information on this can be found at Wikipedia.
Another application for this circuit could be as a Voltage Follower
which has a
Voltage Controllable Time Constant. Perhaps
one might want an envelope with
a slow or fast attack and a fast or slow decay.
some cases the Four-Quadrant spice
simulation might make the data sheet schematic
a little easier to understand.
the Voltage Controlled Resistor application,
being able to simulate using perfect
buffers instead of darlingtons has its advantages. This is especially
true when it comes
to building Voltage Controlled Capacitors and Voltage Controlled Inductors.
Floating Voltage Controlled Resistor
functions just fine with the darlington
1.2V offsets. The simulation of this circuit shows why. To see the
resistor in action, the example needs to be put into a resistor
_/\ /\ /\_ OUT0
__/\ /\ /\__
| \/ \/ _|_
\ /| |
| |\ VOUT1
\ \// __/
|__|_/\/\/ | |
| | \/\/\_|__| \__
\___/ | \
| \/\/\ |_______/|\_| __|
/\/\/ | / |
| \| \|
|/ |/ |
|_____/\ /\ /\__|_/\ /\ /\_|____/\
VOUT0 \/ \/ 1NN0 \/
\/ INN1 \/ \/
With IABC going from 1mA to zero, the floating resistor appears to be
from 10K Ohms to Open. The wave forms below shows that.
But any type of Voltage Controlled Impedance can be made using OTAs.
A Voltage Controlled Negative Resistor can
cancel out the current loading
of a Load Resistor. And a Voltage Controlled Negative Capacitor can
out stray capacitance to greatly improve speed.
The State Variable Filters are by
far the most beautiful of all the filters.
Different filters can be made simply by changing voltage feedback. For
instance a Bessel
filter has a set of feedbacks such that a low pass filter
signal is not shaped distorted. If maximally flat gain is required,
feedback can be adjusted to form a Butterworth
Regardless of type of filter, the frequency response is independently
over up to maybe 5 orders of magnitude for the LM13600 (not LM13700) and
may get as high a 10-12 orders of magnitude in frequency if it were
built in BiCMOS
circuit above can come in very handy in a
lab which tends to have
a shortage of equipment. The LM13600 output stage allows this circuit
to have almost a 1Hz to 1Mhz frequency range. This circuit can fill in
for a lab function generator in most applications. Of course to have a
function generator, there should also be a
sine wave output.
The wide dynamic range of bipolar transistor maybe very under
For a LM13600, almost 6 orders of magnitude in current range mean having
almost 6 orders of magnitude in control over timing. Given that
BiCMOS are much faster and perhaps have 10 to 12 orders of magnitude,
could there be some timing applications
which could use this performance?
There are a whole class of nonlinear relationships that one encounters
electronics to the real world. The Schmitt Trigger application was an
investigate this area. The following are some of these nonlinear
under their common system names.
limited Saturation is of course the
natural nonlinearity of OTAs.
This nonlinearity together with other types of nonlinearity may allow
good modeling of a saturating magnetic core.
Preloaded means something is under
stress without an external load.
one is called Spring Hardening.
This is called Dead Zone.
Toggle which is also the schmitt trigger
application has memory
of its past input signal built in. Combining this feature with some of
nonlinearities may allow close modeling of magnetic components.