ANALOG DEVICES Audio Dual Matched NPN Transistor SSM-2210 FEATURES * Very Low Voltage Noise ............. @ 100Hz, 1nV/VHz MAX * Excellent Current Gain Match ..............cssssssers 0.5% TYP Tight Vig Match (V5) ..sscsssssssesssssessesseeeseeseees 200i.V MAX Outstanding Offset Voltage Drift .............. 0.03nV/C TYP High Gain-Bandwidth Product ................000 200MHz TYP * Low Cost Direct Replacement For LM394BN/CN ORDERING INFORMATION t PACKAGE OPERATING PLASTIC so TEMPERATURE 8-PIN 8-PIN RANGE SSM2210P $sm2210s' XIND* * XIND = 40C to +85C t For availability on SO package, contact your local sales office. GENERAL DESCRIPTION The SSM-2210 is a dual NPN matched transistor pair specifi- cially designed to meet the requirements of ultra-low noise au- dio systems. With its extremely low input base spreading resistance (rbb is typically 28Q), and high current gain (h,, typically exceeds 600 @|, = 1mA), systems implementing the SSM-2210 can achieve outstanding signal-to-noise ratios. This will result in superior performance compared to systems incorporating commerciaily available monolithic amplifiers. The equivalent input voltage noise of the SSM-2210 is typically only 0.8nV/VHz over the entire audio bandwidth of 20Hz to 20KHz. Excellent matching of the current gain (Ah...) to about 0.5% and low Vag of less than 50,V (typical) make it ideal for symmetri- cally balanced designs which reduce high order amplifier har- monic distortion. Stability of the matching parameters is guaranteed by protec- tion diodes across the base-emitter junction. These diodes pre- vent degradation of Beta and matching characteristics due to reverse biasing of the base-emitter junction. The SSM-2210 is also an ideal choice for accurate and reliable current biasing and mirroring circuits. Furthermore, since a cur- rent mirror's accuracy degrades exponentially with mismatches of V,,'s between transistor pairs, the low Vog of the SSM-2210 will preclude offset trimming in most circuit applications. The SSM-221 0 is offered in an 8-pin epoxy DIP and 8-pin SO, its performance and characteristics are guaranteed over the ex- tended industrial temperature range of -40C to +85C. PIN CONNECTIONS 8-PIN PLASTIC DIP (P-Suffix) | | 8-PIN SO (S-Suffix) | | | ABSOLUTE MAXIMUM RATINGS Collector Current (1) ....seeceeiseeteetieeeenteteneeeees 20mA Emitter Current (1p)... ie nite renters 20mA Collector-Collector Voltage (BV__) ose 40V Collector-Base Voitage (BV nag). reenter 40V Collector-Emitter Voltage (BV ..) cee 40V Emitter-Emitter Voltage (BV)... eecceeseeene tents renee: 40V Operating Temperature Range .......... 40C to +85C Storage Temperature 00.0.0 eeeteeereteees -65C to +125C Junction Temperature 0... eee rere -65C to +150C Lead Temperature (Soldering, 60 sec) .0....... +300C PACKAGE TYPE @,, (NOTE 1) e UNITS 8-Pin Plastic DIP (P) 110 50 C/w 8-Pin SO (S) 160 44 CW NOTE: 1. @, is specified for worstcase mounting conditions, i.e... , is specified for device in socket for P-DIP packages; @ , is specified for device soldered to printed circuit board for SO packages.SSM-2210 ELECTRICAL CHARACTERISTICS at V., = 15V, |, = 10HA, T, = 25C, unless otherwise noted. SSM-2210 PARAMETER SYMBOL CONDITIONS MIN Typ MAX UNITS . |. = 1mA (Note 1) 300 605 - c Current Gain Nee lc = 10uA 200 550 . Current Gain Match Ane 10pA < In <1mA (Note 2) - 0.5 5 % Ie =1mA, Vop =0 (Note 3) f, = 10Hz - 1.6 2 Noise Voitage Density e, f, = 100Hz - 0.9 1 aVNAZ f= TkKHz - 0.85 1 t= 10kHz - 0.85 1 Offset Voltage Vv Vou =9 - 10 200 Vv 9 os I, = 1mA HM Oftset Voltage O<V..V, (Note 4) V_/AV CB~ MAX _ 10 Change vs Veg Wos/4Vcp 1HAS|,<1mA (Note 5) 50 HV Offset Voltage Change Vn, =0V AV. /Al cB - 7 vs Collector Current osc 1pA <i, <1mA (Note 5) 5 0 HV Breakdown Voltage BV oEG 40 - ~ Vv Gain-Bandwidth Product f, I, = 10MA, Vag = 10V - 200 - MHz Coilector-Base | Vag = V - 2 Leakage Current C80 CBU MAX S 500 pA Collector-Collector Van =V, N 7 - Leakage Current lee co = Vax (Notes 6, 7) 35 500 pA Collector-Emitter Vac=V, (Notes 6, 7) t CE MAX _ 35 A Leakage Current CES Vee 79 500 p Input Bias Current lb 1, = 10pA - - 50 nA Input Offset Current log Io = 10HA - - 6.2 nA Collector Saturation i,=1tmA Vv c - 0.05 . Vv Voltage CE(SAT) |, = 100A 02 Output Capacitance Cop Vog= 15V, |, =0 - 23 - pF Bulk Resistance ae 10uA < \, <10mA (Note 6) - 0.3 1.6 Q Collector-Collector Von 20 - 35 - F Capacitance See ce p NOTES: 1. Current gain is guaranteed with Collector-Base Voltage (V.,) swept from 0 to v at the indicated collector currents. MAX 2. Current Gain Match (4h,,) is defined as: Ange ~ { c 100(Alg) (Neemin) 3. Noise Voltage Density is guaranteed, but not 100% tested. 4. This is the maximum change in Vos aS Vog iS Swept from OV to 40V. 5. Measured at |, = 10HA and guaranteed by design over the specified range of |. 6. Guaranteed by design. 7. lee and lees are verified by measurement of logo:SSM-2210 ELECTRICAL CHARACTERISTICS at Vog = 15V, 40C <T, < +85C, unless otherwise noted. SSM-2210 PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS |. = 1mA (Note 1) 300 - - Cc Current Gain Nee |, = 10uA 200 _ _ Offset Voltage Vv Vog=0 - 220 Vv g os |,=1mA 4 Average Offset Tcv 10pA < l. <1imA,0< Veg < Vax (Note 2) - 0.08 1 uvec Voltage Drift os Vag Trimmed to Zero (Note 3) - 0.03 0.3 Input Bias Current \, |, = 10pA - ~ 50 nA Input Offset Current log I, = 10nA - - 13 nA Input Offset Current Drift TClos |, = 10HA (Note 4) - 40 150 pac Collector-Base Leakage Current 'cB0 Vee = Vax ~ 3 ~ nA Collector-Emitter ( Vig =Via. Vac = - - Leakage Current CES ce = Ywax: Vee = 0 4 na Collector-Collector , VoeV _ 4 aA Leakage Current ce co MAX NOTES: 1. Current gain is guaranteed with Collector-Base Voltage (V_,) swept from 0 to Visax at the indicated collector current. Vv, 2. Guaranteed by V,,, test (TCV, = Se Vag): T = 298K for T, = 25C. 3. The initial zero offset voltage is established by adjusting the ratio of i,, tol, at T, =25C. This ratio must be held to 0.003% over the entire temperature range. Measurements are taken at the temperature extremes and 25C. 4. Guaranteed by design. TYPICAL PERFORMANCE CHARACTERISTICS LOW FREQUENCY NOISE NOISE FIGURE vs EMITTER-BASE (0.1 Hz TO 10 Hz) COLLECTOR CURRENT LOG CONFORMITY 15 0.4 " i} 14 Ty = 25C Vog = 0V 13 Re = thf Fy = TkHz Ty = +25C : > 12 0.3 8 " = 5 gr = = a? s 0.2 ce 5 8 Q Ww i 7 3 | / a6 0.1 + 2 5 8 : a 4 3 0 t t= 1s/DIV 2 1 [Ry = 10Kn2 0 -0.1 i 0.001 0.01 o1 1.0 10 1077 10 1073 to 107? COLLECTOR CURRENT (mA) COLLECTOR CURRENT (A)SSM-2210 TYPICAL PERFORMANCE CHARACTERISTICS NOISE VOLTAGE NOISE VOLTAGE DENSITY NOISE CURRENT DENSITY vs FREQUENCY vs COLLECTOR CURRENT DENSITY vs FREQUENCY 15 Ta = 928C: Ta = 425C Vee = 5V _ Vee= 5V g g Z|. : z 10H & E Z Z 2 i 10 Ps ZZ) & 6 uw er LL & g 3 5 5 5 3 Q 100Hz Q wy ~ "| 3 8 g . 0.5 0.1 1 10 100 Th 10k 100k Q 3 6 9 12 0.1 1 10 100 th 10k 100k FREQUENCY (Hz) COLLECTOR CURRENT (mA) FREQUENCY (Hz) TOTAL NOISE vs CURRENT GAIN vs CURRENT GAIN COLLECTOR CURRENT COLLECTOR CURRENT vs TEMPERATURE 900 900 Rg Rg 300 Vee = OV 300 Ig 2 1mA 700 700 ~ f= 1kHz uw w 5 600 > ,* 3 3 00 3 2 3 o (EXCLUDES |, ) . 300 200 200 100 0.001 0.01 01 1 *o.001 0.01 O41 1 on ~25 25 75 125 175 COLLECTOR CURRENT (mA} COLLECTOR CURRENT (mA) TEMPERATURE (C) BASE-EMITTER-ON- SMALL-SIGNAL INPUT GAIN BANDWIDTH VOLTAGE vs COLLECTOR RESISTANCE vs COLLECTOR vs COLLECTOR CURRENT CURRENT CURRENT 1000 o7 TTT 00 Ta 2 925C Vee = 5V A = 10 5 100 0.6 i = a a 8 ZG 10 Tos y g 38 La Soon ze = an z vr" \ r 1 0.4 2 0.01 0.1 0.3 LL iis 0.001 : a 0.001 0.01 O41 1 10 100 0.001 0.01 0.1 1 10 0.001 0.01 0.1 1 10 100 COLLECTOR CURRENT (mA) COLLECTOR CURRENT (mA) COLLECTOR CURRENT (mA)SSM-2210 TYPICAL PERFORMANCE CHARACTERISTICS Continued SMALL-SIGNAL OUTPUT CONDUCTANCE vs COLLECTOR CURRENT SATURATION VOLTAGE vs COLLECTOR CURRENT 1000 Neg = 5 3 100 e 3 2 1 Z 3 eo z 5 2 = 01 3 2 yo 4 0.01 0.01 0.001 0.01 0.1 1 10 100 0.001 0.01 0.4 1 10 COLLECTOR CURRENT (mA) COLLECTOR CURRENT (mA) COLLECTOR-BASE COLLECTOR-TO-COLLECTOR CAPACITANCE vs CAPACITANCE vs COLLECTOR- REVERSE BIAS VOLTAGE TO-SUBSTRATE VOLTAGE 50 Ta 3 25C ne = 425C 40 : 3M 5 BIN s g a a . & 10 0 10 20 wo 4 50 0 10 20 Ko) 40 50 COLLECTOR-TO-SUBSTRATE VOLTAGE (VOLTS) REVERSE BIAS VOLTAGE (VOLTS) COLLECTOR-TO-COLLECTOR CAPACITANCE vs REVERSE BIAS VOLTAGE 25 Ta = 425C 2.0 & w wi 2 15 Z E \ E g 3 = NK < < 1.0 3 es | w oe 0s 0 0 10 20 30 40 50 9 REVERSE BIAS VOLTAGE (VOLTS) COLLECTOR-TO-BASE LEAKAGE vs TEMPERATURE 100 =z & so41 3 2 0.1 0.01 25 50 75 100 1 TEMPERATURE (C) COLLECTOR-TO-COLLECTOR LEAKAGE vs TEMPERATURE 100 10 = g = 1 3 8 Ss 0.01 25 50 75 100 +P} TEMPERATURE (C) EMITTER-BASE CAPACITANCE vs REVERSE BIAS VOLTAGE Te = 028C 20 x 4 50 REVERSE BIAS VOLTAGE (VOLTS)SSM-2210 + oa <= COMPENSATION 2000, 0-001uF O.1pF < WHEY YYW #8 YW #8 R, GAIN s( " +1 R, {[10k02 1 1 =(1. 1 \ayes Ce * sa * Ri, = 19K0 R, = 10920 FIGURE 1: A Low-Noise Wideband Amplifier A VERY LOW-NOISE, WIDEBAND AMPLIFIER Figure 1 illustrates a low-noise, wide-band amplifier consisting of a high slew rate JFET amplifier, the OP-44, and a cascoded differential preamplifier using the SSM-2210 transistor pair. The SSM-2210 achieves extremely low input voltage noise perform- ance (e, = 0.7nV/VHz) via a large geometry transistor design which minimizes the base-spreading resistance. This, however, results in relatively higher collector-to-base capacitance (C_,) than ordinary small-signal transistors. For high gain stages, the Miller effect of C_,, will limit the voltage gain bandwiath; resort- ing to a cascode configuration reduces the Miller feedback ca- pacitance, improving stability, bandwidth, and reducing distor- tion due to base-width modulation. Additionally, cascoding does not increase the noise figure of the overall amplifier system and reduces the high order harmonic distortion. The circuit in Figure 1 balances the impedance symmetrically in the differential preamp. This serves to reject common-mode noise injected from the power supplies. Although the SSM-2210's transistors are closely matched, an offset voltage error can still be created by imbalanced source impedances. Accordingly, a precision low-power amplifier (OP- 97), configured as anoninverting integrator is implemented which servos-out the offset voltage to less than 100pV referred to the input of the amplifier.SSM-2210 Rte Tart a ae Lt? LOM MOISE OP. v=#20 Vout: ieip-p 25 FEB 29 15:74:40 OL . ee ee Hee ce ee ey i i t ' I | 7 NS Oe a; | e001 -- wo a FIGURE 2: Spectrum Analyzer Display of Wideband Amplifier Noise Spectral Density. e, = 1.7nVNAZ Figure 2 illustrates the composite amplifier's low voltage noise density of only 1.7nV/VHz @ 1kHz. Figure 3 and Figure 4 show the excellent pulse response and an extremely low distortion of only 0.0015% over the audio bandwidth, respectively. FIGURE 4: Total Harmonic Distortion vs Frequency FIGURE 5: D./.M. vs Frequency A special test was performed to check for dynamic or transient intermodulation distortion. A square wave of 3.15kHz is mixed with a sine wave probe tone, and the resulting intermodulation distortion was found to be less than 0.002% (Figure 5). This is an impressively low value considering the amplifier's gain of 26GB. Interestingly, the GBW product of the composite amplifier was 63MHz which is much larger than that of the OP-44 by itself. This is made possible by the SSM-2210's cascoded preampii- fier having a wide bandwidth and large signal gain. The measured performance of this amplifier is summarized in Table 1. TABLE 1: Measured Performance of the Low-Noise Wideband Amplifier Slew-Rate 40V/us Gain-Bandwidth 63.6 MHz Input Noise Voltage Density @ 1kHz 1.7nV/NAz Output Voltage Swing +13V Input Offset Voltage 10unVSSM-2210 500pV/VHz AMPLIFIER In situations where low output, low-impedance transducers are used, amplifiers must have very low voltage noise to maintain a good signal-to-noise ratio. The design presented in this applica- tion is an operational amplifier with only 500pV/VHz of broad- band noise. The front end uses SSM-2210 low-noise dual tran- sistors to achieve this exceptional performance. The op amp has superb DC specifications compatible with high-precision trans- ducer requirements, and AC specifications suitable for profes- sional audio work. PRINCIPLE OF OPERATION The design configuration in Figure 6 uses an OP-27 op amp (already a low-noise design) preceded by an amplifier consist- ing of three paraliel-connected SSM-2210 dual transistors. Base spreading resistance (rbb) generates thermal noise which is reduced by a factor of V3 when the input transistors are parallel connected. Schottky noise, the other major noise-generating mechanism, is minimized by using a relatively high collector current (1mA per device). High current ensures a low dynamic emitter resistance, but does increase the base current and its associated current noise. Higher current noise is relatively un- important when low-impedance transducers are used. +N O SSM-2210 FIGURE 6: Simplified SchematicSSM-2210 CIRCUIT DESCRIPTION The detailed circuit is shown in Figure 7. A total input-stage emitter current of 6mA is provided by Q,. The transistor acts as a true current source to provide the highest possible common-mode rejection. R,, R,, and R, ensure that this current splits equally among the three input pairs. The constant current in Q, is set by using the forward voltage of a GaAsP light-emitting diode as a reference. The difference between this voltage and the base- emitter voltage of a silicon transistor is predictable and constant (to within a few percent) over the military temperature range. The voltage difference, approximately 1V, is impressed across the emitter resistor R,, which produces a temperature-stable emit- ter current. R, and C, provide phase compensation for the amplifier and are sufficient to ensure stability at gains of ten and above. R, is an input offset trim that provides approximately +300V trim range. The very low drift characteristics of the SSM-2210 make it possible to obtain drifts of less than 0.14.V/C when the offset is nulled close to zero. If this trim is not required, the R,,R,, and R, network should be omitted and R.,/R, connected directly to V+. +15V a, 3A 2a > x0 NULL AA r RS Ry >A L scone 2] 1000. > * 1MQ0% SS cS NSKI.0.1% T s 1 rw i aN 15300 o.otut opzr >! }s OUTPUT Vt -----4--- | 4 | NO -IN 1 | | 100nF tt._-fPpo_ P_ _ | | semen JT --a44---------+4- | | | R , $ 2000 4 ! > m0 | Lt--LEEP TL _ | | ssmzao ee a ee ee | | sr. | 32000 | tou PEP _ _ _ | ssmzo >A u FIGURE 7: Complete Amplifier SchematicSSM-2210 AMPLIFIER PERFORMANCE The measured performance of the op ampis summarized in Table 2. Figure 8 shows the broadband noise spectrum which is flat at about 500pV/VHz. Figure 9 shows the low-frequency spectrum which illustrates the low 1/f noise corner at 1.5Hz. The low-fre- quency characteristic in the time domain from 0.1Hz to 10Hz is shown in Figure 10; peak-to-peak amplitude is less than 40nV. TABLE 2: Measured Performance of the Op Amp Input Noise Voltage Density at 1kHz 500pV/VHz Input Noise Voltage from 0.1Hz to 10Hz 40nV,,, Input Noise Current at 1kHz 1.5pA/VHz G=10 3MHz Gain-Bandwidth G=100 600kHz G = 1000 150kHz Siew Rate 2V/us Open-Loop Gain 3x 107 Common-Mode Rejection 130dB Input Bias Current 3uA Supply Current 10mA Nulled TCV 4, 0.1nV/C Max T.H.D. at 1kKHz G = 1000 0.002% FIGURE 8: Spectrum Analyzer Display Broadband ae Suz ee rs FIGURE 9: Spectrum Analyzer Display Low Frequency FIGURE 10: Oscilloscope Display CONCLUSION Using SSM-2210 matched transistor pairs operating at a high current level, itis possible to construct a high-performance, low- noise operational amplifier. The circuit uses a minimum of com- ponents and achieves performance levels exceeding monolithic amplifiers.SSM-2210 Yao (0 to 10) a vj 2 ovo Fi -15 AAA R= TEL LABS Q81E (+0.35%/C) FIGURE 11: Fast Logarithmic Amplifier FAST LOGARITHMIC AMPLIFIER The circuit of Figure 11 is a modification of a standard logarith- mic amplifier configuration. Running the SSM-2210 at2.5mA per side (full-scale) allows a fast response with wide dynamic range. The circuit has a 7 decade current range, a 5 decade voltage range, and is capable of 2.5ys settling time to 1% witha 1 to 10V step. The output follows the equation: Vo = Rg + Re kT In Vaer Ro 4G Vin Tocompensate for the temperature dependence of the kT/qterm, a resistor with a positive 0.35%/C temperature coefficient is chosen for R,. The output is inverted with respect to the input, and is nominally 1V/decade using the component values indicated.