ca3160t Intersil Corporation, ca3160t Datasheet - Page 8

• Manufacturer Part Number: ca3160t
• Description: 4mhz, Bimos Operational Amplifier With Mosfet Input/cmos Output
• Manufacturer: Intersil Corporation

Typical Applications
Voltage Followers
Operational amplifiers with very high input resistances, like
the CA3160, are particularly suited to service as voltage
followers. Figure 3 shows the circuit of a classical voltage
follower, together with pertinent waveforms using the CA3160
in a split-supply configuration.
A voltage follower, operated from a single supply, is shown in
Figure 4 together with related waveforms. This follower circuit
is linear over a wide dynamic range, as illustrated by the
reproduction of the output waveform in Figure 4B with input-
signal ramping. The waveforms in Figure 4C show that the
follower does not lose its input-to-output phase-sense, even
though the input is being swung 7.5V below ground potential.
This unique characteristic is an important attribute in both
operational amplifier and comparator applications. Figure 4C
also shows the manner in which the COS/MOS output stage
permits the output signal to swing down to the negative
supply-rail potential (i.e., ground in the case shown). The
digital-to-analog converter (DAC) circuit, described in the
following section, illustrates the practical use of the CA3160 in
a single supply voltage follower application.
9-Bit CMOS DAC
A typical circuit of a 9-bit Digital-to-Analog Converter (DAC) (see
Note 6) is shown in Figure 5. This system combines the concepts
of multiple-switch CMOS lCs, a low-cost ladder network of
discrete metal-oxide-film resistors, a CA3160 op amp connected
as a follower, and an inexpensive monolithic regulator in a simple
single power-supply arrangement. An additional feature of the
DAC is that it is readily interfaced with CMOS input logic, e.g.,
10V logic levels are used in the circuit of Figure 5.
The circuit uses an R/2R voltage-ladder network, with the output-
potential obtained directly by terminating the ladder arms at
either the positive or the negative power supply terminal. Each
CD4007A contains three inverters, each inverter functioning as a
single-pole double-throw switch to terminate an arm of the R/2R
network at either the positive or negative power-supply terminal.
The resistor ladder is an assembly of 1% tolerance metal-oxide
film resistors. The five arms requiring the highest accuracy are
assembled with series and parallel combinations of 806,000
resistors from the same manufacturing lot.
A single 15V supply provides a positive bus for the CA3160
follower amplifier and feeds the CA3085 voltage regulator. A
“scale-adjust” function is provided by the regulator output control,
set to a nominal 10V level in this system. The line-voltage
regulation (approximately 0.2%) permits a 9-bit accuracy to be
maintained with variations of several volts in the supply. The
flexibility afforded by the CMOS building blocks simplifies the
design of DAC systems tailored to particular needs.
NOTE:
6. “Digital-to-Analog Conversion Using the Intersil CD4007A
COS/MOS lC”, Application Note AN6080.
8
CA3160, CA3160A
FIGURE 4B. OUTPUT WAVEFORM WITH GROUND REFERENCE
FIGURE 4C. OUTPUT SIGNAL WITH INPUT SIGNAL RAMPING
FIGURE 4. SINGLE SUPPLY VOLTAGE FOLLOWER WITH
BW (-3dB) = 4MHz
SR = 10V/ s
10k
SINE WAVE INPUT
ASSOCIATED WAVEFORMS. (e.g., FOR USE IN
SINGLE SUPPLY D/A CONVERTER; SEE FIGURE 9
IN AN6080)
3
2
Bottom Trace: Input
Top Trace: Output
FIGURE 4A.
+
CA3160
-
1
0.1 F
2k
5
7
4
OFFSET
ADJUST
+15V
6
0.01 F