Analog Buffer and Inverter Switching with logic -
del20016
Here the 4053 selects or routes the voltage, current or resistance
measurements
to the A-D converter or display. It is selected with the mode selection
when
you want to measure Volts, Amps, Ohms and AC-DC. Some have to be
polarity
inverted and some signals just buffered this is selected and done by
this
circuit according to the digital control.
Now U1 OP07 circuit is a Buffer unity gain and low offset, U2 circuit
is unity gain but polarity of output is opposite of input. D1-D2-R3
form a AND gate to select diode-buzzer test mode. The digital selection
of 4053 Analog-Switch does not produce any errors in the
analog-switching of even mV signals. But it works best at +/- 7.5V dual
supply pin-16 is +7.5V, pin- 8 is digital ground and pin 7 alone should
go to -7.5. Analog ground can be same as digital ground, or the
switched signals must be within +/-5V of digital ground. The switches
should not carry any current and should be buffered at the output by
FET opamps 1-Tera-Ohm. Then alone measurements are ok, as the switches
have ohmic resistance.
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