|NE5230D||Low voltage operational amplifier|
|NE5230D Datasheet PDF : 18 Pages |
NE5230, SA5230, SE5230
What this means is that several instruments, such as a chart
recorder, a meter, or a controller, as well as a long cable, can
be connected in series on the loop and still obtain accurate
readings if the total resistance does not exceed 650 W.
Furthermore, any variation of resistance in this range will
not change the output current.
Any voltage output type transducer can be used, but one
that does not need external DC voltage or current excitation
to limit the maximum possible load resistance is preferable.
Even this problem can be surmounted if the supply power
needed by the transducer is compatible with the NE5230.
The power goes up the line to the transducer and amplifier
while the transducer signal is sent back via the current output
of the NE5230 transconductance configuration.
The voltage range on the input can be changed for
transducers that produce a large output by simply increasing
the current sense resistor to get the corresponding 4.0 to
20 mA output current. If a very long line is used which
causes high line resistance, a current repeater could be
inserted into the line. The same configuration of Figure 7 can
be used with exception of a resistor across the input and line
ground to convert the current back to voltage. Again, the
current sensing resistor will set up the transconductance and
the part will receive power from the line.
A variation on the previous circuit makes use of the supply
current control pin. The voltage present at this pin is
proportional to absolute temperature (PTAT) because it is
produced by the amplifier bias current through an internal
resistor divider in a PTAT cell. If the control pin is connected
to the input pin, the NE5230 itself can be used as a
temperature transducer. If the center tap of a resistive pot is
connected to the control pin with one side to ground and the
other to the inverting input, the voltage can be changed to
give different temperature versus output current conditions
(Figure 8). For additional control, the output current is still
proportional to the input voltage differential divided by the
current sense resistor.
When using the NE5230 as a temperature transducer, the
thermal considerations in the previous section must be kept
1. IOUT = VIN/RC
≈ V REMOTE
For RC = 1W
Figure 8. NE5230 remote temperature transducer utilizing 4.0 − 20 mA current transmission. This application
shows the use of the accessibility of the PTAT cell in the device to make the part, itself, a transducer.
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