AN142 Audio Circuits Using the NE5532/3/4 Author 1984 Oct

INTEGRATED CIRCUITS

AN142 Audio circuits using the NE5532/3/4 author 1984 Oct

Philips Semiconductors Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

AUDIO CIRCUITS USING THE NE5532/33/34 actually five individual active filters with the same feedback design The following will explain some of Philips Semiconductors low noise for all five. The main difference in all five stages is the values of C5 op amps and show their use in some audio applications. and C6, which are responsible for setting the center frequency of each stage. Linear pots are recommended for R9. To simplify use of this circuit, a component value table is provided, which lists center DESCRIPTION frequencies and their associated capacitor values. Notice that C5 The 5532 is a dual high-performance low noise operational amplifier. equals (10) C6, and that the Value of R8 and R10 are related to R9 Compared to most of the standard operational amplifiers, such as by a factor of 10 as well. The values listed in the table are common the 1458, it shows better noise performance, improved output drive and easily found standard values. capability and considerably higher small-signal and power bandwidths. RIAA EQUALIZATION AUDIO PREAMPLIFIER This makes the device especially suitable for application in high USING NE5532A quality and professional audio equipment, instrumentation and With the onset of new recording techniques with sophisticated control circuits, and telephone channel amplifiers. The op amp is playback equipment, a new breed of low noise operational amplifiers internally-compensated for gains equal to one. If very low noise is of was developed to complement the state-of-the-art in audio prime importance, it is recommended that the 5532A version be reproduction. The first ultra-low noise op amp introduced by Philips used which has guaranteed noise voltage specifications. Semiconductors was called the NE5534A. This is a single operational amplifier with less than 4nV/√Hz input noise voltage. The NE5534A is internally-compensated at a gain of three. This device APPLICATIONS has been used in many audio preamp and equalizer (active filter) The Philips Semiconductors 5532 High-Performance Op Amp is an applications since its introduction early last year. ideal amplifier for use in high quality and professional audio equipment which requires low noise and low distortion. Many of the amplifiers that are being designed today are DC-coupled. This means that very low frequencies (2-15Hz) are The circuit included in this application note has been assembled on being amplified. These low frequencies are common to turntables a PC board, and tested with actual audio input devices (Tuner and because of rumble and tone arm resonances. Since the amplifiers Turntable). It consists of an RIAA (Recording Industry Association of can reproduce these sub-audible tones, they become quite America) preamp, input buffer, 5-band equalizer, and mixer. objectionable because the speakers try to reproduce these tones. Although the circuit design is not new, its performance using the This causes non-linearities when the actual recorded material is 5532 has been improved. amplified and converted to sound waves. The RIAA preamp section is a standard compensation configuration The RIAA has proposed a change in its standard playback response with low frequency boost provided by the Magnetic cartridge and the curve in order to alleviate some of the problems that were previously RC network in the op amp feedback loop. Cartridge loading is discussed. The changes occur primarily at the low frequency range accomplished via R1. 47k was chosen as a typical value, and may with a slight modification to the high frequency range (See Figure differ from cartridge to cartridge. 2). Note that the response peak for the bass section of the playback The Equalizer section consists of an input buffer, 5 active variable curve now occurs at 31.5Hz and begins to roll off below that band pass/notch (depending on R9’s setting) filters, and an output frequency. The roll-off occurs by introducing a fourth RC network summing amplifier. The input buffer is a standard unity gain design with a 7950µs time constant to the three existing networks that providing impedance matching between the preamplifier and the make up the equalization circuit. The high end of the equalization equalizer section. Because the 5532 is internally-compensated, no curve is extended to 20kHz, because recordings at these external compensation is required. The 5-band active filter section is frequencies are achievable on many current discs.

C5 Equ In 5 C1 RIAA Out + RIAA 3 7 R7 R8 R7 + 1/2 5532 1 R5 6 1/2 5532 – 2 R9 C6 R9 R1 – R5 R11

R2 R3 2 – C7 R10 + 1 6 FLAT C2 C3 1/2 5532 – TO VOL./ 3 7 + 1/2 5532 BAL AMP 5 + EQUALIZE R4 REPEAT ABOVE CIRCUIT C4 FOR DESIRE NO. OF STAGES.

R12 SL00850 Figure 1. RIAA - Equalizer Schematic

1984 Oct 2 August 1988 Rev: 2 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

COMPONENT VALUES FOR FIGURE 1 R8=25k R8=50k R8=100k R7=2.4k R9=240k R7=5.1k R9=510k R7=10k R9=1meg

fO C5 C6 fO C5 C6 fO C5 C6 23Hz 1µF 0.1µF 25Hz 0.47µF 0.047µF 12Hz 0.47µF 0.047µF 50Hz 0.47µF 0.047µF 36Hz 0.33µF 0.033µF 18Hz 0.33µF 0.033µF 72Hz 0.33µF 0.033µF 54Hz 0.22µF 0.022µF 27Hz 0.22µF 0.022µF 108Hz 0.22µF 0.022µF 79Hz 0.15µF 0.015µF 39Hz 0.15µF 0.015µF 158Hz 0.15µF 0.015µF 119Hz 0.1µF 0.01µF 59Hz 0.1µF 0.01µF 238Hz 0.1µF 0.01µF 145Hz 0.082µF 0.0082µF 72Hz 0.082µF 0.0082µF 290Hz 0.082µF 0.0082µF 175Hz 0.068µF 0.0068µF 87Hz 0.068µF 0.0068µF 350Hz 0.068µF 0.0068µF 212Hz 0.056µF 0.0056 µF 106Hz 0.056µF 0.0056µF 425Hz 0.056µF 0.0056µF 253Hz 0.047µF 0.0047µF 126Hz 0.047µF 0.0047µF 506Hz 0.047µF 0.0047µF 360Hz 0.033µF 0.0033µF 180Hz 0.033µF 0.0033µF 721Hz 0.033µF 0.0033µF 541Hz 0.022µF 0.0022µF 270Hz 0.022µF 0.0022µF 1082Hz 0.022µF 0.0022µF 794Hz 0.015µF 0.0015µF 397Hz 0.015µF 0.0015µF 1588Hz 0.015µF 0.0015µF 1191Hz 0.01µF 0.001µF 595Hz 0.01µF 0.001µF 2382Hz 0.01µF 0.001µF 1452Hz 0.0082µF 820pF 726Hz 0.0082µF 820pF 2904Hz 0.0082µF 820pF 1751Hz 0.0068µF 680pF 875Hz 0.0068µF 680pF 3502Hz 0.0068µF 680pF 2126Hz 0.0056µF 560pF 1063Hz 0.0056µF 560pF 4253Hz 0.0056µF 560pF 2534Hz 0.0047µF 470pF 1267Hz 0.0047µF 470pF 5068Hz 0.0047µF 470pF 3609Hz 0.0033µF 330pF 1804Hz 0.0033µF 330pF 7218Hz 0.0033µF 330pF 5413Hz 0.0022µF 220pF 2706Hz 0.0022µF 220pF 10827Hz 0.0022µF 220pF 7940Hz 0.0015µF 150pF 3970Hz 0.0015µF 150pF 15880Hz 0.0015µF 150pF 11910Hz 0.001µF 100pF 5955Hz 0.001µF 100pF 23820Hz 0.001µF 100pF 14524Hz 820pF 82pF 7262Hz 820pF 82pF 17514Hz 680pF 68pF 8757Hz 680pF 68pF 21267Hz 560pF 56pF 10633Hz 560pF 56pF 12670Hz 470pF 47pF 18045Hz 330pF 33pF

–25 OLD RIAA –20

–15

–10 NEW RIAA –5

(db)5

1 10 100 (HZ) 1K 10K 100K SL00851 Figure 2. Proposed RIAA Playback Equalization

1984 Oct 3 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

–15V

.1µF .27µF – INPUT + 3 8 TO LOAD 47K NE5532A 1 4 2 + – .1µF –15V

+ 49.9K SL00853 49.9 Figure 4.

.056µF 4.99K Assume a signal input square wave with dV/dt of 250V/µs and 2V peak amplitude as shown. If a 22pF compensation capacitor is 47µF inserted and the R1 C1 circuit deleted, the device slew rate falls to .015µF approximately 7V/µs. The input waveform will reach 2V/250V/µs or 8ns, while the output will have changed (8×10-3) only 56mV. The NOTE: differential input signal is then (VIN-VO) RI/RI+RF or approximately All resistors are 1% metal film. SL00852 1V. Figure 3. RIAA Phonograph Preamplifier Using The diode limiter will definitely be active and output distortion will the NE5532A occur; therefore, VIN<1V as indicated. Next, a sine wave input is used with a similar circuit. NE5533/34 DESCRIPTION The slew rate of the input waveform now depends on frequency and the 5533/5534 are dual and single high-performance low noise the exact expression is operational amplifiers. Compared to other operational amplifiers, dv such as TL083, they show better noise performance, improved + 2w cos wt dt output drive capability and considerably higher small-signal and power bandwidths. The upper limit before slew rate distortion occurs for small-signal This makes the devices especially suitable for application in high (VIN<100mV) conditions is found by setting the slew rate to 7V/µs. quality and professional audio equipment, instrumentation and That is: control circuits, and telephone channel amplifiers. 7 x 106Vńms + 2w cos wt The op amps are internally-compensated for gain equal to, or higher than, three. The frequency response can be optimized with an at ωt = 0 external compensation capacitor for various applications (unity gain 6 amplifier, capacitive load, slew rate, low overshoot, etc.) If very low 7x10 6 wLIMIT + + 3.5x10 radńs noise is of prime importance, it is recommended that the 2 5533A/5534A version be used which has guaranteed noise 3.5x106 f + [ 560kHz specifications. LIMIT 2p

APPLICATIONS Diode Protection of Input The input leads of the device are protected from differential transients above ±0.6V by internal back-to-back diodes. Their presence imposes certain limitations on the amplifier dynamic characteristics related to closed-loop gain and slew rate. Consider the unity gain follower as an example:

1984 Oct 4 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

External Compensation Network Improves dV/dt Bandwidth +2 By using an external lead-lag network, the follower circuit slew rate and small-signal bandwidth can be increased. This may be useful in situations where a closed-loop gain less than 3 to 5 is indicated. A number of examples are shown in subsequent figures. The principle benefit of using the network approach is that the full slew rate and bandwidth of the device is retained, while impulse-related –2V parameters such as damping and phase margin are controlled by VIN = 2 Sin ωt choosing the appropriate circuit constants. For example, consider 1K the following configuration:

22pF 1K

NE 5534

SL00854 Figure 5.

5 22pF Rj – C 2V C 0 2 8 R1 NE 5534 0 C1 6 –VO –Vi 3 + ∆t1 ∆t2 SL00855 Figure 6.

1 GAIN 90 1K

–

R LAG 45 NETWORK NE5534 C

SL00856 0 Figure 7. 0 0.1 1.0 10 50 MHz SL00857 Figure 8.

1984 Oct 5 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

PHASE applications because of their high gain and easily-tailored frequency 0 response.

RIAA PREAMP USING THE NE5534 The preamplifier for phono equalization is shown in Figure 14 with the theoretical and actual circuit response. θ –90o Low frequency boost is provided by the inductance of the magnetic cartridge with the RC network providing the necessary break points to approximate the theoretical RIAA curve. LAG NETWORKS

–180o 0 0.1 1.0 10 50 RUMBLE FILTER MHz SL00858 Following the amplifier stage, rumble and scratch filters are often Figure 9. used to improve overall quality. Such a filter designed with op amps The major problem to be overcome is poor phase margin leading to uses the 2-pole Butterworth approach and features switchable break instability. points. With the circuit of Figure 15, any degree of filtering from fairly sharp to none at all is switch-selectable. By choosing the lag network break frequency one decade below the unity gain crossover frequency (30-50MHz), the phase and gain margin are improved. An appropriate value for R is 270Ω. Setting TONE CONTROL the lag network break frequency at 5MHz, C may be calculated Tone control of audio systems involves altering the flat response in 1 order to attain more low frequencies or more high ones, dependent C + 6 2p @ 270 @ 5x10 upon listener preference. The circuit of Figure 16 provides 20dB of + 118pF bass or treble boost or cut as set by the variable resistance. The actual response of the circuit is shown also.

RULES AND EXAMPLES BALANCE AND LOUDNESS AMPLIFIER Compensation Using Pins 5 and 8 (Limited Figure 17 shows a combination of balance and loudness controls. Due to the non-linearity of the human hearing system, the low Bandwidth and Slew Rate) frequencies must be boosted at low listening levels. Balance, level, A single-pole and zero inserted in the transfer function will give an and loudness controls provide all the listening controls to produce ° added 45 of phase margin, depending on the network values. the desired music response. Calculating the Lead-Lag Network 1 RIN C1 + Let R1 + VOLTAGE AND CURRENT OFFSET 2p F1 R1 10 ADJUSTMENTS where Many IC amplifiers include the necessary pin connections to provide 1 external offset adjustments. Many times, however, it becomes F1 + (UGBW) 10 necessary to select a device not possessing external adjustments. UGBW + 30MHz Figures 18, 19, and 20 suggest some possible arrangements for off-circuitry. The circuitry of Figure 20 provides sufficient current External Compensation for Wide-Band into the input to cancel the bias current requirement. Although more Voltage-Follower simplified arrangements are possible, the addition of Q2 and Q3 provide a fixed current level to Q1, thus, bias cancellation can be Shunt Capacitance Compensation provided without regard to input voltage level. 1 CF + ,FF [ 30MHz 2p FF RF or 2 – CDIST CF [ 6 ACL VOUT 3 8 VIN + CDIST ≈ Distributed Capacitance ≈ 2 - 3pF NOTES 5 Many audio circuits involve carefully-tailored frequency responses. C1 = CC(1) C1 Pre-emphasis is used in all recording mediums to reduce noise and CC = 22pF for NE5533/34 C = 22pF [See graph under typical performance characteristics] produce flat frequency response. The most often used de-emphasis C SL00859 curves for broadcast and home entertainment systems are shown in Figure 13. Operational amplifiers are well suited to these Figure 10. Unity Gain Non-Inverting Configuration

1984 Oct 6 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

RF CF

RIN 2 R VIN – F 6 VOUT 3 R + 8 IN – 5 VIN C1 C1 V SL00860 OUT Figure 11. Unity Gain Inverting Configuration R1

NOTE: Input diodes limit differential to <0.5V SL00861 Figure 12. External Compensation for Wideband Voltage Follower

1984 Oct 7 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

30 40 TURN OVER FREQUENCIES 25 TURN OVER FREQUENCIES 50Hz, 500Hz, 2122Hz 35 50Hz, 3180Hz 20 TIME CONSTANTS TIME CONSTANTS 15 3150µs 30 3150µs 318µs 50µs 75µs 10 25

5 20 0

–5 15 RELATIVE GAIN (dB) RELATIVE RELATIVE GAIN 9dB) RELATIVE –10 10 –15 5 –20

–25 0

–30 10 100 1K 10K 100K 10 100 1K 10K 100K FREQUENCY (Hz) FREQUENCY (Hz) a. RIAA Equalization b. NAB Standard Playback 71/2 IPS 40 TURN OVER FREQUENCIES 35 50Hz, 1326Hz TIME CONSTANTS 30 3150µs 125µs 25

RELATIVE GAIN (dB) RELATIVE 10

10 100 1K 10K 100K FREQUENCY (Hz) c. 3.75 IPS Tape Equalization

25 5 TURN OVER FREQUENCY 1kHz TURN OVER FREQUENCY 2122 CPS µ 20 TIME CONSTANT 75 s 0

15 –5 10

–10 5

0 –15

–5 –20 RELATIVE GAIN (dB) RELATIVE

–10 GAIN (dB) RELATIVE –25 –15

–30 –20

–25 –35 10 100 1K 10K 100K 10 100 1K 10K 100K FREQUENCY (Hz) FREQUENCY (Hz) d. Base Treble Curve e. Standard FM Broadcast Equalization SL00862 Figure 13.

1984 Oct 8 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

–15V

0.22 INPUT +

NE5534 OUTPUT RSL 1.1M –

1.1K –15V

20µF 100K 1M RIAA NAB

750pF 0.0033

NOTES: 1.1M *Select to provide specified transducer loading. ≥ Output Noise 0.8mVRMS (with input shorted) 16K 0.003

All resistor values are ohms. a.

70 70 BODE PLOT 60 60

50 50 ACTUAL RESPONSE BODE PLOT 40 ACTUAL 40 RESPONSE

30 30 GAIN — dB GAIN — dB 20 20

10 10 0 0 101 102 103 104 105 101 102 103 104 105 FREQUENCY (Hz) FREQUENCY (Hz)

b. Bode Plot of RIAA Equalization and the Response c. Bode Plot of NAB Equalization and the Response Realized in the Actual Circuit Using the 531. Realized in an Actual Circuit Using the 531. SL00863 Figure 14. Preamplifier - RIAA/NAB Compensation

1984 Oct 9 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

20K 1

10K 2 – – 6.8K 3 100 0.1 0.1 NE5534 0022 NE5534 + 4 +

220k 1

75k 2 20K

47k 3 10K 0056 27k 4 6.8K

39k

22k 20K

13k 10K

6.8K

RUMBLE 6.8K 330pF SCRATCH POSITION FREQ. POSITION FREQ. 1 FLAT 1 5KHz 2 30MHz 2 10MHz 3 50HZ 3 15HZ NOTE: 4 80Hz 4 FLAT All resistor values are in ohms. SL00864 Figure 15. Rumble/Scratch Filter

1µF +140 10K 100K 10K MAX MAX INPUT +30 BASS TREBLE BOOST BOOST +20 0.033µF 0.033µF V+ +10 10K 0 + OUTPUT A 5V GAIN (dB) –10 – PEAK TO PEAK 3.3K –20 0.033µF 0.033µF 68K MAX MAX V– –30 BASS TREBLE CUT CUT 100K –40 10 100 1,000 10,000 100,000 NOTES: FREQUENCY (Hz) 1. Amplifier A may be a NE531 or 301. Frequency compensation, as for unity gain non-inverting amplifiers, must be used. 2. Turn-over frequency - 1kHz. 3. Base boost +20dB, bass cut -20dB, treble boost +19dB at 20Hz, treble cut -19dB at 20Hz.

All resistor values are in ohms. SL00865 Figure 16. Tone Control Circuit for Operational Amplifiers

1984 Oct 10 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

100K

0.5 A IN – LEVEL 1/2 5533 100K + 220pF – 100K 1/2 A OUT 5533 4.7K 120 LOUDNESS + IN BALANCE OUT 26K 1.2K

4.7K .33 100K 100K

0.5 B IN – 1/2 100K 5533 + 220pF – 100K 1/2 B OUT 1290 5533 +

1.2K

.33 100K

NOTE: All resistor values are in ohms. SL00866 Figure 17. Balance Amplifier with Loudness Control

R3 +V R3

INPUT R1 200K R4 + R4 R3 – 50K OUTPUT NE5534 OUTPUT NE5534 R2 – + R1 100 100K R2 R5 RANGE = V V ( R ) 50K 1 R2 RANGE = V ( ) INPUT R5 R2 R1 GAIN = 1 + 100 NOTE: R4 = R2 All resistor values are in ohms. SL00868 Figure 19. Universal Offset Null for Non-Inverting Amplifiers SL00867 Figure 18. Universal Offset Null for Inverting Amplifiers

1984 Oct 11 Philips Semiconductors Application note

Audio circuits using the NE5532/3/4 AN142

V+ BIAS CURRENT COMPENSATION

R3 R1

Q1 –

NE5534 EOUT E + SELECT R2 AND R3 IN FOR DESIRED CURRENT V– SL00869 Figure 20. Bias Current Compensation

1984 Oct 12