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