Blackmer
®
Pre-Trimmed IC
Voltage Controlled Amplifiers
THAT
2180A, 2180B, 2180C
FEATURES
• Wide Dynamic Range: >120 dB
• Wide Gain Range: >130 dB
• Exponential (dB) Gain Control
• Low Distortion: < 0.01 % (2180A)
• Wide Gain-Bandwidth: 20 MHz
• Dual Gain-Control Ports (pos/neg)
• Pin-Compatible with 2150-Series
APPLICATIONS
• Faders
• Panners
• Compressors
• Expanders
• Equalizers
• Filters
• Oscillators
• Automation Systems
Description
THAT 2180 Series integrated-circuit voltage
controlled amplifiers (VCAs) are very high-
performance current-in/current-out devices
with two opposing-polarity, voltage-sensitive
control ports. They offer wide-range exponen-
tial control of gain and attenuation with low
signal distortion. The parts are trimmed at
wafer stage for low THD and control-voltage
feedthrough without further adjustment.
The VCA design takes advantage of a fully
complementary dielectric isolation process
which offers closely matched NPN/PNP pairs, to
deliver discrete performance at IC prices. The
parts are available in three grades, selected for
factory trimmed distortion, allowing the user to
optimize cost vs. performance. The 2180 Series
is available in an 8-pin single-in-line (SIP)
package.
Pin Name
Input
7
Pin Number
1
2
3
4
5
6
7
8
2k
Vcc
Ec+
Ec-
BIAS CURRENT
COMPENSATION
2
Sym
V-
Gnd
V+
Output
Ec+
25
Vbe
MULTI-
PLIER
Ec-
3
8
Input
1
6
Output
4
Gnd
Iadj
Sym
Table 1. Pin assignments
Max THD @ 1V,
1 kHz, 0 dB
Plastic SIP
5
V-
Iset
0.01%
0.02%
0.05%
2180AL08-U
2180BL08-U
2180CL08-U
Figure 1. 2180-series equivalent circuit diagram
Table 2. Ordering information
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright © 2008, THAT Corporation
Document 600029 Rev 02
Document 600029 Rev 02
Page 2 of 12
THAT 2180 Series
Blackmer® Pre-trimmed IC VCAs
SPECIFICATIONS
1
Absolute Maximum Ratings
2,3
Positive Supply Voltage (V
CC
)
Negative Supply Voltage (V
EE
)
Supply Current (I
CC
)
Maximum
∆E
C
E
C+
- (E
C-
)
+20 V
-20 V
10 mA
±1V
Power Dissipation (P
D
) (T
A
= 75 ºC)
Operating Temperature Range (T
OP
)
Storage Temperature Range (T
ST
)
330 mW
0 to +70 ºC
-40 to +125 ºC
Recommended Operating Conditions
Parameter
Positive Supply Voltage
Symbol
V
CC
Conditions
2180A
Min Typ Max
+4
-4
V
CC
- V
EE
= 30 V
I
SET
= 2.4 mA
1
—
+15
-15
2.4
0.35
+18
-18
5
1.5
2180B
Min Typ Max
+4
-4
1
—
+15
-15
2.4
0.35
+18
-18
5
1.5
2180C
Min Typ Max
+4
-4
1
—
+15
-15
2.4
0.35
+18
-18
5
1.5
Units
V
V
mA
mA
rms
Negative Supply Voltage V
EE
Bias Current
Signal Current
I
SET
I
IN
+ I
OUT
Electrical Characteristics
2
2180A
Parameter
Supply Current
Equiv. Input Bias Current
Input Offset Voltage
Output Offset Voltage
Symbol
I
CC
I
B
V
OFF(IN)
V
OFF(OUT)
Conditions
No signal
No Signal
No Signal
R
out
= 20 kΩ
0 dB gain
+15 dB gain
+30 dB gain
Min
—
—
—
—
—
—
—
Typ
2.4
2
±5
0.5
1
3
20
Max
4
10
—
1
3
12
—
Min
—
—
—
—
—
—
—
2180B
Typ
2.4
2
±5
1
1.5
5
20
Max
4
12
—
2
4
15
—
Min
—
—
—
—
—
—
—
2180C
Typ
2.4
2
±5
1.5
3
9
20
Max
4
15
—
3
10
30
—
Units
mA
nA
mV
mV
mV
mV
µA
Gain Cell Idling Current
Gain-Control Constant
I
IDLE
T
A
=25°C (T
CHIP
≅35°C)
-60 dB < gain < +40 dB
Pin 2 (Fig. 14)
E
C+
/Gain (dB)
Pin 3
E
C-
/Gain (dB)
∆E
C
/∆T
CHIP
Ref T
CHIP
= 27°C
-60 to +40 dB gain
6.0 6.1
-6.2 -6.1
6.2
-6.0
6.0 6.1
-6.2 -6.1
6.2
-6.0
6.0 6.1
-6.2 -6.1
6.2 mV/dB
-6.0 mV/dB
%/°C
%
dB
Gain-Control TempCo
Gain-Control Linearity
1 kHz Off Isolation
Output Noise
— +0.33 —
—
0.5
115
2
—
— +0.33 —
—
110
0.5
115
2
—
— +0.33 —
—
110
0.5
115
2
—
E
C+
= -360mV,E
C-
=+360mV 110
e
n(OUT)
20 Hz ~ 20 kHz
R
out
= 20kΩ
0 dB gain
+15 dB gain
No Signal
—
—
-98
-88
-97
-86
-2.6
—
—
-98
-88
-96
-85
-2.5
—
—
-98
-88
-95
-84
-2.6
dBV
dBV
V
Voltage at V-
V
V-
-3.1 -2.85
-3.1 -2.85
-3.1 -2.85
1. All specifications are subject to change without notice.
2. Unless otherwise noted, T
A
=25ºC, V
CC
=+15V, V
EE
= -15V.
3. Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only; the functional operation of
the device at these or any other conditions above those indicated in the operational sections of this specification is not impli ed. Exposure to absolute maximum rating condi-
tions for extended periods may affect device reliability.
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright © 2008, THAT Corporation
THAT 2180 Series
Blackmer® Pre-trimmed IC VCAs
Page 3 of 12
Document 600029 Rev 02
Electrical Characteristics (con’t)
2
Parameter
Symbol
Conditions
1 kHz, No External Trim
V
IN
= 0 dBV, 0 dB gain
— 0.005 0.010
— 0.010 0.020
— 0.030 0.040
— 0.030 0.040
—
12
—
+0.15
— 0.030 0.050
— 0.040 0.070
— 0.040 0.070
—
-0.2
12
0.0
—
+0.2
%
%
%
V/µs
dB
2180A
Min Typ Max
2180B
Min Typ Max
2180C
Min Typ Max
Units
Total Harmonic Distortion THD
V
IN
= +10 dBV, -15 dB gain — 0.020 0.030
V
IN
= -5 dBV, +15 dB gain
Slew Rate
Gain at 0 V Control Voltage
R
IN
= R
OUT
= 20 kΩ
E
C-
= 0 mV
— 0.020 0.030
—
-0.1
12
0.0
—
+0.1
-0.15 0.0
Vcc
2180
Series
VCA
IN
10u
20k
1
Ec-
7
V+
-IN
GND
V-
22p
20k
OUT
8
3
Ec-
SYM
Ec+
-
OP275
5
6
2
4
OUT
NC
+
Power Supplies
Vcc = +15 V
Vee = -15 V
5.1k
Vee
Figure 2. Typical Application Circuit
Figure 3. 2180-series Frequency Response vs. Gain
Figure 4. 2180-series Noise (20kHz NBW) vs. Gain
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright © 2008, THAT Corporation
Document 600029 Rev 02
Page 4 of 12
THAT 2180 Series
Blackmer® Pre-trimmed IC VCAs
Theory of Operation
4
The THAT 2180 Series VCAs are designed for
high performance in audio-frequency applications
requiring exponential gain control, low distortion,
wide dynamic range and low control-voltage
feedthrough. These parts control gain by converting
an input current signal to a bipolar logged voltage,
adding a dc control voltage, and reconverting the
summed voltage back to a current through a bipolar
antilog circuit.
Figure 5 presents a considerably simplified inter-
nal circuit diagram of the IC. The ac input signal
current flows in pin 1, the input pin. An internal
operational transconductance amplifier (OTA) works
to maintain pin 1 at a virtual ground potential by
driving the emitters of Q1 and (through the Voltage
Bias Generator) Q3. Q3/D3 and Q1/D1 act to log the
input current, producing a voltage, V3, which repre-
sents the bipolar logarithm of the input current. (The
voltage at the junction of D1 and D2 is the same as
V3, but shifted by four forward V
be
drops.)
Figure 6. Gain vs. Control Voltage (E
C+
, Pin 2) at 25
°
C
Gain Control
Since pin 8, the output, is usually connected to a
virtual ground, Q2/D2 and Q4/D4 take the bipolar
antilog of V3, creating an output current which is a
precise replica of the input current. If pin 2 (Ec+)
and pin 3 (Ec-) are held at ground, the output
current will equal the input current. For pin 2
positive or pin 3 negative, the output current will be
scaled larger than the input current. For pin 2
negative or pin 3 positive, the output current is
scaled smaller than the input.
Figure 7. Gain vs. Control Voltage (E
C-
, Pin 3) at 25
°
C
Figure 8. Gain vs. Control Voltage (E
C-
) with Temp (
°
C)
In normal operation, the output current is
converted to a voltage via an opamp-based I-V
converter, as shown in Figure 2, where the conver-
sion ratio is determined by the feedback resistor
connected between the output and inverting input.
The signal path through the VCA and the output
opamp is non-inverting.
The scale factor between the output and input
currents is the gain of the VCA. Either pin 2 (Ec+) or
pin 3 (Ec-), or both, may be used to control gain.
Gain is exponentially proportional to the voltage at
pin 2, and exponentially proportional to the negative
of the voltage at pin 3. Therefore, pin 2 (Ec+) is the
positive
control port, while pin 3 (Ec-) is the
Figure 5. Simplified Internal Circuit Diagram
4. For more details about the internal workings of the 2180 Series of VCAs, see An
Improved Monolithic Voltage-Controlled
Amplifier,
by Gary K. Hebert (Chief Technology Officer, for THAT Corporation), presented at the 99th convention of the
Audio Engineering Society, New York, Preprint number 4055.
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright © 2008, THAT Corporation
THAT 2180 Series
Blackmer® Pre-trimmed IC VCAs
Page 5 of 12
Document 600029 Rev 02
negative
control port. Because of the exponential
characteristic, the control voltage sets gain
linearly
in decibels.
Figure 6 shows the decibel current gain
of a 2180 versus the voltage at Ec+, while Figure 7
shows gain versus the Ec-.
DC Bias Currents
The 2180 current consumption is determined by
the resistor between pin 5 (V-) and the negative
supply voltage (V
EE
). Typically, with 15V supplies, the
resistor is 5.1 kΩ, which provides approximately
2.4 mA. This current is split into two paths: 570
μA
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
μA
biases the core
transistors (Q1 through Q4), the rest is available for
input and output signal current.
Temperature Effects
The logging and antilogging in the VCA depends
on the logarithmic relationship between voltage and
current in a semiconductor junction (in particular,
between a transistor's V
be
and I
c
). As is well known,
this relationship is temperature dependent. There-
fore, the gain of any log-antilog VCA depends on its
temperature.
Figure 8 shows the effect of temperature on the
negative control port. (The positive control port behaves
in the same manner.) Note that the gain at Ec = 0 V is
0 dB, regardless 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 2180's gain characteristic is
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
Gain
=
E
C+
−
E
C−
(0.0061)(1+0.0033
T)
,
Eq. 1
where
∆T
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
=
E
C+
−
E
C−
0.0061
,
Eq. 2
Figure 9. Representative DC Offset vs. Gain
If only the positive control port is used, this
becomes
Audio Performance
The 2180-Series VCA design, fabrication and
testing ensure extremely good audio performance
when used as recommended. In particular, the 2180
maintains low distortion over a wide range of gain,
cut and signal levels. Figures 10 through 12 show
typical distortion performance for representative
samples of each grade of the part. Figure 13 shows
the harmonic content of the distortion in a typical
B-grade part.
Gain
=
E
C+
0.0061
,
Eq. 3
If only the negative control port is used, this
becomes
Gain
=
E
C−
0.0061
,
Eq. 4
THAT Corporation; 45 Sumner Street; Milford, MA 01757-1656; USA
Tel: +1 508 478 9200; Fax: +1 508 478 0990; Web: www.thatcorp.com
Copyright © 2008, THAT Corporation
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