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PDF THAT2181 Data sheet ( Hoja de datos )
| Número de pieza | THAT2181 | |
| Descripción | Voltage Controlled Amplifiers | |
| Fabricantes | THAT Corporation | |
| Logotipo |  |
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T H AT Corporation
FEATURES
· Wide Dynamic Range: >120 dB
· Wide Gain Range: >130 dB
· Exponential (dB) Gain Control
· Low Distortion:
~0.0025% (typical 2181A)
~0.005% (typical 2181C)
· Wide Gain-Bandwidth: 20 MHz
· Dual Gain-Control Ports (pos/neg)
· Pin-Compatible with 2150-Series
Trimmable IC
Voltage Controlled Amplifiers
THAT 2181A, 2181B, 2181C
APPLICATIONS
· Faders
· Panners
· Compressors
· Expanders
· Equalizers
· Filters
· Oscillators
· Automation Systems
Description
THAT 2181 Series integrated-circuit voltage con-
trolled amplifiers (VCAs) are very high-performance
current-in/current-out devices with two oppos-
ing-polarity, voltage-sensitive control ports. They offer
wide-range exponential control of gain and attenuation
with low signal distortion. The parts are selected after
packaging based primarily on after-trim THD and con-
trol-voltage feedthrough performance.
The VCA design takes advantage of a fully comple-
mentary dielectric isolation process which offers
closely matched NPN/PNP pairs. This delivers perfor-
mance unobtainable through any conventional pro-
cess, integrated or discrete. The parts are available in
three grades, allowing the user to optimize cost vs.
performance. Both 8-pin single-in-line (SIP) and sur-
face mount (SO) packages are available.
BIAS CURRENT
COMPENSATION
Input
1
6
Gnd
7
2k Vcc
Vbe
MULTI-
PLIER
2
Ec+
25
Ec-
3
8
Output
4
Sym
Iadj
Iset
V-
5
Figure 1. 2181 Series Equivalent Circuit Diagram
Pin Name
Input
SIP Pin
1
SO Pin
1
Ec+ 2 2
Ec– 3 3
Sym
44
V– 5 5
Gnd 6 6
V+ 7 7
Output
8
8
Table 1. 2181 Series Pin Assignments
Max Trimmed THD Plastic Plastic
@1 V, 1 kHz, 0 dB SIP
SO
0.005%
2181LA 2181SA
0.008%
2181LB 2181SB
0.02%
2181LC 2181SC
Table 2. Ordering Information
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Document 600030 Rev 01
1 page  
600030 Rev 01
Page 5
ship is temperature dependent. Therefore, the gain of
any log-antilog VCA depends on its temperature.
Figure 8 shows the effect of temperature on the nega-
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.
Mathematically, the 2181's gain characteristic is
Gain =
EC+ - EC-
,
(0.0061)(1 + 0.0033DT)
Eq. 1
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 = EC+ - EC- ,
0.0061
Eq. 2
If only the positive control port is used, this becomes
Gain = EC+ ,
0.0061
Eq. 3
If only the negative control port is used, this becomes
Gain = -EC- ,
0.0061
Eq. 4
DC Bias Currents
The 2181 current consumption is determined by the
resistor between pin 5 (V-) and the negative supply voltage
(VEE). Typically, with 15V supplies, the resistor is 5.1 kW,
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.
Trimming
The 2181-Series VCAs are intended to be adjusted for
minimum distortion by applying a small variable offset
voltage to pin 4, the SYM pin. Note that there is a 25 W re-
sistor internal to the 2181 between pin 4 and pin 2. As
shown in Figure 2, Page 3, the usual method of applying
this offset is to use the internal 25 W resistor along with a
larger value resistor to form a voltage divider connected
to the wiper of a trim pot across the supply rails.
This trim should be adjusted for minimum harmonic
distortion. This is usually done by applying a mid-
dle-level, middle-frequency signal (e.g. 1 kHz at 1 V) to
the audio input, setting the VCA to 0 dB gain, and adjust-
ing the SYM trim while observing THD at the output. In
the 2181, this adjustment coincides closely with the set-
ting which produces minimum control-voltage
feedthrough, though the two settings are not always iden-
tical.
DC Feedthrough
Normally, a small dc error term flows in pin 8 (the
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
Figure 10. 1 kHz THD+Noise Vs. Input Level, 0 dB Gain
Figure 11. 1 kHz THD+Noise Vs. Input Level, +15 dB
Gain
Figure 9. Representative DC Offset Vs. Gain
Figure 12. 1 kHz THD+Noise Vs. Input Level, -15 dB
Gain
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
5 Page | ||
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