that2180a THAT Corporation, that2180a Datasheet - Page 5

• Manufacturer Part Number: that2180a
• Description: Pre-trimmed Ic Voltage Controlled Amplifiers
• Manufacturer: THAT Corporation

600029 Rev 01
tive control port. (The positive control port behaves in the
same manner.) Note that the gain at Ec = 0 V is 0 dB, re-
gardless of temperature. Changing temperature changes
the scale factor of the gain by 0.33%/°C, which pivots the
curve about the 0 dB point.
DC Bias Currents
resistor between pin 5 (V-) and the negative supply voltage
(V
which provides approximately 2.4 mA. This current is
split into two paths: 570 mA is used for biasing the IC,
and the remainder becomes Icell as shown in Figure 5.
Icell is further split in two parts: about 20 mA biases the
core transistors (Q1 through Q4), the rest is available for
input and output signal current
DC Feedthrough
output). When the gain is changed, the dc term changes.
This control-voltage feedthrough is more pronounced
with gain; the –A version of the part produces the least
feedthrough, the –C version the most. See Figure 9 for
typical curves for dc offset vs. gain
Audio Performance
ensure extremely good audio performance when used as
EE
Figure 8 shows the effect of temperature on the nega-
Mathematically, the 2180's gain characteristic is
Gain
where DT is the difference between room temperature
(25°C) and the actual temperature, and Gain is the
gain in decibels. At room temperature, this reduces to
Gain
If only the positive control port is used, this becomes
Gain
If only the negative control port is used, this becomes
Gain
The 2180 current consumption is determined by the
Normally, a small dc error term flows in pin 8 (the
The 2180-Series VCA design, fabrication and testing
). Typically, with 15V supplies, the resistor is 5.1 kW,
Figure 9. Representative DC Offset Vs. Gain
=
=
=
=
(0.0061)(1
E
0.0061
0.0061
-
E
C
0.0061
E
+
C
C
+
-
-
E
E
,
,
C
C
+
-
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
+
-
,
0.0033DT)
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Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
C
-
,
Eq. 1
Eq. 2
Eq. 3
Eq. 4
recommended. In particular, the 2180 maintains low
distortion over a wide range of gain, cut and signal lev-
els. Figures 10 through 12 show typical distortion per-
formance for representative samples of each grade of the
part. Figure 13 shows the harmonic content of the dis-
tortion in a typical B-grade part.
Figure 10. 1 kHz THD+Noise Vs. Input Level, 0 dB Gain
Figure 13. FFT of THD, 0dB gain, 1kHz, 0dBV,
Figure 12. 1 kHz THD+Noise Vs. Input Level,
Figure 11. 1 kHz THD+Noise Vs. Input Level,
Typical 2180B
+15 dB Gain
-15 dB Gain
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