Rohm BA6110 Voltage controlled operational amplifier Datasheet

BA6110FS
Standard ICs
Voltage controlled operational amplifier
BA6110FS
The BA6110FS is a low-noise, low-offset programmable operational amplifier. Offering superb linearity over a broad
range, this IC is designed so that the forward direction conductivity (gm) can be changed, making it ideal for applications
such as voltage control amplifiers (VCA), voltage control filters (VCF) and voltage control oscillators (VCO).
Distortion reduction circuitry improves the signal-to-noise ratio by a significant 10dB at a distortion rate of 0.5% in
comparison with products not equipped with this feature. When used as a voltage control amplifier (VCA), a high S / N
ratio of 86dB can be achieved at a distortion rate of 0.5%.
The open loop gain is determined by the control current and an attached gain determining resistance RL, enabling a wide
range of settings.
In addition, a built-in low-impedance output buffer circuit reduces the number of attachments.
!Applications
Electronic volume controls
Voltage-controlled impedances
Voltage-controlled amplifiers (VCA)
Voltage-controlled filters (VCF)
Voltage-controlled oscillators (VCO)
Multipliers
Sample holds
Schmitt triggers
!Features
1) Low distortion rate.
(built-in distortion reduction bias diode)
2) Low noise.
3) Low offset voltage. (VIO = 3m VMax).
4) Built-in output buffer.
5) Variable gm with superb linearity across three decade
fields.
N.C.
VCC
BUFFER OUTPUT
N.C.
BUFFER INPUT
VCA OUTPUT
N.C.
– VEE
!Block diagram
16
15
14
13
12
11
10
9
BA6110FS
1/2
–
BUFFER
+
1/2
1
2
3
4
5
6
7
8
POSITIVE INPUT
N.C.
NEGATIVE INPUT
N.C.
INPUT BIAS
N.C.
CONTROL INPUT
N.C.
VCC
BA6110FS
Standard ICs
!Internal circuit configuration
11
12
Buffer IN
Positive input 1
D1
D2
Current mirror (4)
15
Current mirror (3)
Current mirror (1)
Current mirror (2)
OUT
Q13
R4
VCC
R5
14
Buffer OUT
Q14
Q17
Negative input 3
Q18
5
Input bias
Q6
Q5
Q3
Q1
Q9 Q10 Q12
Q7
Q4
Q2
R3
R2
Current mirror (5)
R1
Q8
Q11
Q15
Q16
9
Control pin
VEE
Fig.1
7
!Absolute maximum ratings (Ta = 25°C)
Parameter
Symbol
Limits
Unit
VCC
V
Pd
34
300∗1
mW
Topr
– 20 ~ + 70
˚C
Storage temperature
Tstg
– 55 ~ + 125
˚C
Maximum control current
IC Max.
500
µA
Power supply voltage
Power dissipation
Operating temperature
*1 Reduced by 3mW for each increase in Ta of 1˚C each 25˚C.
!Electrical characteristics (unless otherwise noted, Ta = 25°C, VCC = 15V, VEE = – 15V)
Parameter
Quiescent current
Symbol
Min.
Typ.
Max.
IQ
0.9
3.0
6.0
Unit
Conditions
mA ICONTROL = 0µA
Measurement
circuit
Fig.2
Pin 7 bias current
I7PIN
—
0.8
5
µA
Distortion
THD
—
0.2
1
%
ICONTROL = 200µA, VI = 5mVrms
—
Fig.2
Fig.2
µs
ICONTROL = 500µA
Fig.2
Pin 6 maximum output voltage
| VOM6 |
12
14
—
V
ICONTROL = 500µA
Fig.2
Pin 8 maximum output voltage
| VOM8 |
9
11
—
V
RL = 47kΩ
Fig.2
Pin 6 maximum output current
| IOM6 |
300
500
650
µA
ICONTROL = 500µA
Fig.2
Forward transmission conductance
gm
4800 8000 12000
Residual noise 1
VN1
—
– 94
– 90
ICONTROL = 0µA, BPF
dBm
(30 ~ 320kHz, 3dB, 6dB / OCT)
Residual noise 2
VN2
—
– 74
– 66
dBm
ICONTROL = 200µA, BPF
(30 ~ 20kHz, 3dB, 6dB / OCT)
Fig.2
VNP2
—
10.5
11.5
dB
ICONTROL = 200µA, BPF
(30 ~ 20kHz, 3dB, 6dB / OCT)
Fig.2
L (Leak)
—
– 94
dBm
ICONTROL = 0µA, VIN = – 30dBm
fIN = 20kHz
Fig.2
Discontinuous noise
Leakage level
– 75
Fig.2
BA6110FS
Standard ICs
!Measurement circuit
D.V
S4
27kΩ
10µF
+
mA
1kΩ
1
VCC = + 10V
S5
S1
S0
11
12
2
15
1
1
V
BA6110FS
14
600Ω
3
5
1kΩ
9
S3
1
1V
500µA→
3
S2
7
1
S6-2
47kΩ
S6-1
S7
2
V.V THD DV
1
3
2
200µA→
2
30 ~ 20kHz
BPF
2
1
2 150kΩ
40dB AMP
VEE = – 10V
Vmp
Fig.2
!Circuit discription
The BA6110FS is configured of an operational amplifier
which can control the forward propagation conductance
(gm) using the control current, an input biascompensating diode used to eliminate distortion created
by the amplifier’s differential input, a bias setter, and an
output buffer.
In the operational amplifier, Pin 1 is the positive input and
Pin 3 is the negative input. Pin 7 is the control pin which
determines the differential current. Pin 11 is the output pin
which determines the open loop gain using the external
resistor and the control current.
This section describes the circuit operation of this
operational amplifier.
Transistors Q13 and Q14 form the differential input for the
operational amplifier, while transistors Q7 to Q12 are
composed of the current mirror circuits. The current
mirror absorbs current from the differential input common
emitter which is equal to the control current flowing into
the Pin 7 control pin. If the differential input VIN = 0 at this
point, then 1 / 2 Ic is supplied to the Q13 and Q14
collectors and the other half passes through the current
mirrors (3) and (4). The output of current mirror (3) which
is the differential active load is inverted by current mirror
(5), and is balanced with the output of current mirror (4),
also an active load.
If the differential input changes, the current balance
changes. The output current is on Pin 11. An output
voltage can be generated using an external resistance.
For the open loop gain of this operational amplifier, if the
Pin 7 control current is ICONTROL and the Pin 11 external
resistance is RO, then:
Av = gm · RO =
ICONTROL × RO
KT
2 q
To eliminate the distortion created by the differential input,
the input bias diode and its bias circuit consist of the
following: bias diodes D1 and D2, current mirrors (1) and
(2), and the Pin 5 bias pin current mirror that consists of
the transistors Q1 to Q6 and the resistance R1.
This circuit eliminates the distortion that occurs as a
result of using the differential input open loop.
In the buffer circuit, Pin 12 is the buffer input and Pin 14 is
the buffer output.
In the buffer circuit, the emitter follower consists of the
active load of the NPN transistor, Q17, and its active load,
Q16. The VF difference created by the emitter follower is
eliminated by the emitter follower which consists of the
PNP transistor Q18 and resistor R5. Also, the gain is
determined by the ratio of the signal source resistance
RIN and the diode impedance.
BA6110FS
Standard ICs
!Attached components
(1) Positive input (Pin 1)
This is the differential positive input pin. To minimize the
distortion due to the diode bias, an input resistor is
connected in series with the signal source. By increasing
the input resistance, distortion is minimized.
However, the degree of improvement for resistances
greater than 10kΩ is about the same. An input resistance
of 1kΩ to 20kΩ is recommended.
(2) Negative input (Pin 3)
This is the differential negative input pin. It is grounded
with roughly the same resistance value as that of the
positive input pin. The offset adjustment is also
connected to this pin. Make sure a sufficiently high
resistance is used, so as not to disturb the balance of the
input resistance (see Figure 3).
(3) Input bias diode (Pin 5)
The input bias diode current (ID) is determined by this pin.
The IC input impedance when the diode is biased, if the
diode bias current is ID, is expressed as follows:
Rd =
26
ID (mA)
(Ω)
(4) Control (Pin 7)
This pin controls the differential current. By changing the
current which flows into this pin, the gain of the differential
amplifier can be changed.
(5) Output (Pin 11)
The differential amplifier gain (AV) is determined by the
resistor RO connected between the output terminal and
the Pin 7 control terminal, as follows:
Av = gm · RO =
ICONTROL (mA)
× RO
52 (mV)
Make sure the resistor is selected based on the desired
maximum output and gain.
(6) Buffer input (Pin 12)
The buffer input consists of the PNP and NPN emitter
follower. The bias current is normally about 0.8µA.
Consequently, when used within a small region of control
current, we recommend using the high input impedance
FET buffer.
(7) Buffer output resistance (Pin 14)
An 11kΩ resistor is connected between VCC and the
output within the IC. When adding an external resistance
between the GND and the output, make sure the resistor
RL = 33kΩ.
!Application example
(1) Fig.3 shows a voltage-controlled amplifier (AM
modulation) as an example of an application of the
BA6110FS.
By changing the ICONTROL current on Pin 7, the differential
gain can be changed. The gain (AV), if the resistance of
Pin 11 is RO, is determined by the following equation:
Av = gm · RO =
ICONTROL (mA)
× RO
52 (mV)
Good linearity can be achieved when controlling over
three decades.
By connecting Pin 5 to the VCC by way of a resistor, the
input is biased at the diode and distortion is reduced.
The gain in this case is given by the diode impedance Rd
and the ratio of the input resistance RIN, as shown in the
following:
Av = gm · RO ×
Rd
Rd × RIN
The diode impedance Rd = (26 / ID (mA) ) Ω, so that the
Pin 5 bias current ID = (VCC - 1V) / R (Pin 5). The graph in
Fig. 6 shows the control current in relation to the open
loop gain at the diode bias. In the same way, Fig.7 shows
the control current in relation to the THD = 0.5% output at
the bias point.
Fig. 8 shows a graph of the control current in relation to
the open gain with no diode bias.
Fig. 9 shows a graph of the control current in relation to
the SN ratio.
Fig. 10 shows a graph of the diode bias current in relation
to the SN ratio.
Fig. 11 shows a graph of the power supply voltage
characteristics.
(2) Fig. 4 shows a low pass filter as an example of an
application of the BA6110FS.
The cutoff frequency fO can be changed by changing the
Pin 7 control current.
The cutoff frequency fO is expressed as:
fO =
RA · gm
(R + RA) 2πC
This is attenuated by -6dB / OCT.
Fig. 12 shows a graph of the ICONTROL in relation to the
output characteristics.
(3) Fig. 5 shows a voltage-controlled secondary low
passfilter as an example of an application of the
BA6110FS.
The cutoff frequency fO can be changed by changing
thePin 7 control current.
fO =
RA · gm
(R + RA) · 2πC
This is attenuated by - 12dB / OCT.
Fig. 13 shows a graph of the ICONTROL output
characteristic.
BA6110FS
Standard ICs
VCC = 15V
150k
I0
VIN
5
RIN
15
10k
1
330k
BA6110FS
3
OUT
14
7
100k VR
12
(Offset adjustment)
ICONTROL
11
10k
RIN
30kΩ
9
R0 = 27kΩ
VEE = – 15V
Fig.3 Voltage-controlled amplifier (electronic volume control)
VCC = 15V
VIN
IC
VC
20kΩ
15
7
100k
1
14
BA6110FS
200Ω
OUT
9
3
5
12
VEE = – 15V
11
150pF
R
100k
Fig.4 Voltage control low pass filter
VCC 15V
ICONTROL
VC
20kΩ
15
100kΩ
1
VIN
200
15
100kΩ
1
7
BA6110FS
200Ω
14
3
V
14
3
11
RA
200
100kΩ
100kΩ
11
12
9
5
RA
200Ω
7
BA6110FS
12
9
R
5
2C
200pF
R
C 100pF
VEE
Fig.5 Voltage-controlled secondary low pass filter
15V
BA6110FS
Standard ICs
For diode bias of 200µA
R0 = 27kΩ
0
– 10
R0 = 10kΩ
ID 200µA
+ 15V
ICONTROL
– 20
– 30
+
VIN
– 40
R0 = 27kΩ
15V
5
10 20
VO
–
1
0.5
0.2
0.1
0.05
0.02
1
50 100 200 500 1000
IO = 0
60
5
10
20
50 100 200
5001000
RIN = 50kΩ
ICONTROL = 500µA
RIN = 2kΩ
RIN =
10kΩ
70
60
5
20
10
VCC = 15V
VEE = – 15V
RO = 27kΩ
fin = 1kHz
NOISE B.P.F20Hz ~ 20kHz
ICONTROL = 200µA
SN ratio when THD = 0.5%
50 100 200 500 1mA
BIAS CURRENT: ID (µA)
Fig.10 SN ratio vs. diode bias current
Fig.9 SN ratio vs. control current
VCC = 15V
VEE = – 15V
6pin C = 150pF
VCC = 15V
VEE = – 15V
ICONTROL = 100µA
–4
–8
– 12
ICONTROL = 10µA
6dB / OCT
– 20
VOLTAGE GAIN: GV (dB)
VOLTAGE GAIN: GV (dB)
10 20
80
CONTROL CURRENT: ICONTROL (µA)
– 16
5
ICONTROL = 200µA
50 100 200 500 1mA
0
2
Fig.7 THD 0.5% output control
current characteristics
SIGNAL TO NOISE RATIO: S / N (dB)
SIGNAL TO NOISE RATIO: S / N (dB)
Fig.6 Open loop gain control
current characteristics
70
0
ICONTROL = 100µA
–4
–8
– 12
– 16
ICONTROL = 10µA
– 12dB / OCT
– 20
– 24
– 24
– 28
– 28
100 200 500 1k 2k
5k 10k 20k 50k 100k
FREQUENCY: f (Hz)
Fig.12 Low pass filter characteristics
No diode bias
R0 = 270kΩ
60
R0 = 50kΩ
50
40
30
R0 = 27kΩ
20
R0 = 10kΩ
10
– 10
1
100 200 500 1k 2k
5k 10k 20k 50k 100k
FREQUENCY: f (Hz)
Fig.13 Secondary low pass filter
characteristics
2
5
10 20
50 100 200
500 1000
CONTROL CURRENT: ICONTROL (µA)
CONTROL CURRENT: ICONTROL (µA)
CONTROL CURRENT: ICONTROL (µA)
80
VCC = 15V
VEE = – 15V
RIN = 10kΩ
Io = 0
0
AV VO
VIN
VCC = 15V NOISE B.P.F20 ~ 20kHz
SN ratio when THD = 0.5%
VEE = – 15V
RIN = 10kΩ
RO = 27kΩ
ID = 200µA
fin = 1kHz
R0 = 10kΩ
OPEN LOOP GAIN: GV (dB)
10
Fig.8 Open loop gain control current
characteristics
MAXIMUM OUTPUT VOLTAGE: VOM (V)
R0 = 50kΩ
20
2
VCC = 15V
With diode bias
VEE = – 15V
RIN = 10kΩ
5 ID = 200µA
R0 = 27kΩ
fin = 1kHz
R0 = 50kΩ
2 Output when THD = 0.5%
10
OUTPUT VOLTAGE: VO (Vrms)
VCC = 15V
VEE = – 15V
RIN = 10kΩ
ID = 200µA
10kΩ
OPEN LOOP GAIN: GV (dB)
!Electrical characteristic curves
15
12 R0 = ∞
Pin 8 voltage
10
8
6
4
2
0
–2
–4
–6
–8
– 10
– 12
– 14
±2
±4
VOM
VOM
±6
±8
± 10 ± 12 ± 14
POWER SUPPLY VOLTAGE: VCC (V)
Fig.11 Maximum output voltage vs.
power supply voltage
BA6110FS
Standard ICs
!External dimensions (Units : mm)
BA6110FS
1
8
4.4 ± 0.2
9
0.8
0.15 ± 0.1
1.5 ± 0.1
0.11
6.2 ± 0.3
6.6 ± 0.2
16
0.36 ± 0.1
0.3Min.
0.15
SSOP-A16
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