Newsgroups: sci.space Subject: 2N3421: More neat info Date: 3 Sep 93 18:13:16 +0930 It was reported in the 1993 August 26 2:30 p.m. PDT Mars Observer Mission Status that a 2N3421 transistor failing in both circuits of the Redundant Crystal Oscillator (RXO) could have led to a non-recoverable loss of Mars Observer. These transistors were from the same batch that failed on NOAA-13 during ground testing after Mars Observer was launched (Why they used the same transistors from the same batch in both sides of the redundant circuit beats me. For proper redundancy different batches should have been used, or even better, different manufacturers to prevent this kind of problem). According to Aviation Week and Space Technology (30 August 1993), the RXO was made by Frequency Electronics, Inc., Uniondale, NY and the transistors were made by Unitrode Semiconductor Products 580 Pleasant Street, Watertown, MA 02172 ph (617) 926 0404, fax (617) 924 1235 I have managed to obtain a data sheet for the Unitrode 2N3421 (which is no longer manufactured). From the characteristics, the 2N3421 is a pretty hefty transistor, designed for power applications (it can take a base current up to 1 Amp!). The AW&ST article says the transistor is used for both a voltage regulator and an oven temperature control in the RXO. This transistor has been around since the sixties (why they didn't use a more available transistor with more modern technology, from the seventies at least, beats me). The specifications of the Unitrode device are (some values may be wrong as I have a faxed copy of the data sheet only): POWER TRANSISTORS 3 Amp, 80 V, Planar NPN JAN, JANTZ, & JANTXV 2N3421 Features Description -------- ----------- * Meets MIL-S-1950D/393 Unitrode power transistors provide a * Collector-Base Voltage: up to 125V unique combination of low saturation * Peak Collector Current: 5A voltage, high gain, and fast switching. * High Power Dissipation in TO-5 They are ideally suited for power 15W @ T_C = 100 C supply, pulse amplifier and similar * Fast Switching high frequency power switching applications. Absolute Maximum Ratings ------------------------ Collector-Base Voltage V_CBO 125V Collector-Emitter Voltage V_CEO 80V Emitter-Base Voltage V_EBO 8V D.C. Collector Current I_C 3A Peak Collector Current I_C 5A Power Dissipation 25 C Ambient 1.0W 100 C Case 15W Operating and Storage Temperature Range -65 C to +200 C Electrical Specifications (at 25 C unless noted) ------------------------- Collector-Emitter Breakdown Voltage BV_CEO 80 Vdc min. (I_C = 50mAdc) Collector-Emitter Cutoff Current I_CEX V_EB = 0.5Vdc, V_CE = 120Vdc 0.5 uAdc max. V_EB = 0.5Vdc, V_CE = 120Vdc, T_A = 150 C 50 uAdc max. Collector-Emitter Cutoff Current I_CEO 5.0 uAdc max. (V_CE = 60Vdc) Emitter-Base Cutoff Current I_EBO 0.5 uAdc max. (V_EB = 6Vdc) Emitter-Base Cutoff Current I_EBO 10 uAdc max. (V_EB = 8Vdc) D.C. Current Gain h_FE I_C = 100mAdc, V_CE = 2Vdc 40 min. I_C = 1Adc, V_CE = 2Vdc 40 min., 120 max. I_C = 1Adc, V_CE = 2Vdc, T_A = -55 C 10 min. I_C = 2Adc, V_CE = 2Vdc 30 min. I_C = 5Adc, V_CE = 5Vdc 15 min. Collector-Emitter Saturation Voltage V_CE(sat) I_C = 1Adc, I_B = 0.1 Adc 0.25 Vdc max. I_C = 2Adc, I_B = 0.2 Adc 0.5 Vdc max. Base-Emitter Saturation Voltage V_BE(sat) I_C = 1Adc, I_B = 0.1 Adc 0.6 Vdc min., 1.2 Vdc max. I_C = 2Adc, I_B = 0.2 Adc 0.7 Vdc min., 1.4 Vdc max. Gain Bandwidth Product f_T 40 MHz min., 160 MHz max. I_C = 0.1Adc, V_CE = 10Vdc, f = 20MHz Output Capacitance C_ob 150 pF max. V_CB = 10Vdc, I_E = 0, f = 1MHz Switching Parameters (I_C = 1Adc, I_B1 = -I_B2 = 0.1Adc) Turn-on Time t_on 0.3 us max. Turn-off Time t_off 1.2 us max. Forward Biased Second Breakdown I_s/b V_CE = 5Vdc, t = 60s, T_C = 100 C 3 Adc min. V_CE = 15Vdc, t = 60s, T_C = 100 C 1 Adc min. V_CE = 37Vdc, t = 60s, T_C = 100 C 0.4 Adc min. V_CE = 80Vdc, t = 60s, T_C = 100 C 120 mAdc min. Unclamped Reverse Biased Second Breakdown E_s/b 45 mJ min. I_C = 3Adc, L = 30 mH, Base Open Clamped Reverse Biased Second Breakdown E_s/b 180 mJ min. I_C = 3Adc, L = 40 mH, V_clamp = Rate V_CBO Motorola recommends the 2N5336 as a replacement for the 2N3421. According to the data sheet it is a: Medium-Power NPN Silicon Transistor ...designed for switching and wide band amplifier applications * Low Collector-Emitter Saturation Voltage - V_CE(sat) = 1.2 Vdc (Max) @ I_C = 5.0 Amp * DC current gain specified to 5 Amperes * Excellent safe operating area * Packaged in the compact TO-205AD case for critical space-limited applications Hitting the data books I tried to obtain some other information on this transistor. The best source was the Spring 1968 Transistor D.A.T.A. Book. The list of manufacturers given for the 2N3421 as of Spring 1968 were Texas Instruments Inc., Semiconductor-Components Division P.O. Box 5012, Dallas, Texas 75222 (Component registered with JEDEC by this manufacturer) Bendix Semicon. Division South St., Holmdel, N.J. 07738 National Semiconductor Corp. P.O. Box 443, Danbury, Conn. 06810 Semi-Elements Inc. Saxonburg Boulevard, Saxonburg, Penna. 16056 (New manufacturer) Solid State Products 1 Pingree St., Salem, Mass. 01970 Transitron Electronics Corp. 168 Albion St., Wakefield, Mass. 01880 Texas Instruments Ltd. Manton Lane, Bedford, England I checked an April 1974 National Semiconductor transistor catalog and the 2N3421 was not listed. I couldn't find any Texas Intruments transistor catalogs. Electrical characteristics of the TI and Bendix transistors were given in the D.A.T.A. book. The TI 2N3421 is listed in the Silicon NPN-High Power Transistors section with a note that it is also a Switching type transistor. The specifications are: Max. Thermal Res. (Junction to Case) theta_jc 174 C/W (free air) Max. Coll. Diss. in Free Air @ 25 C P_c 1.0 W Max. Temp. 170-200 C (case) Absolute Max. Ratings @ 25 C I_C 3.0 A I_B 1.0 A BV_CBO 125 V BV_EBO 8.0 V BV_CEO 80 V Max. I_CBO @ Max. V_CB @ 25 C I_CEX .50 uA h_FE Min. (typical) 40 (pulsed) Max. (typical) 120 Bias V_CE 2.0 V I_C 1.0 A Min. Gain Bandwidth Product f_T 40 MHz T_ON = t_r + t_d .30 us The Bendix 2N3421 is listed in the Switching Transistors section. The specs are: Min. Gain Bandwidth Product f_T 40 MHz Max. Rise Time T_ON = t_r + t_d 0.3 us Max. Fall Time T_OFF = t_s + t_f 1.2 us Max. Coll. Diss. in Free Air @ 25 C P_c 15 W (derating starts at 100 C) h_FE Maximum 120 Bias V_CE 2.0 V I_C 1.0 A Max. Sat. Res. .25 ohms Max. C_ob 150 pF Structure NPN Material Silicon Max. Temp. 200 C (case) The 2N3421 comes in the TO-5 case with the Emitter connected to pin 1, the Base connected to pin 2, and the Collector connected to pin 3 and the case. The TO-5 is a circular case and has the following dimensions: Can diameter (bottom) 0.335 to 0.370 inches (8.51 to 9.40 mm) Can diameter (top) 0.305 to 0.335 inches (7.75 to 8.51 mm) Can height 0.240 to 0.260 inches (6.10 to 6.60 mm) Can lip height 0.010 to 0.030 inches (0.25 to 0.76 mm) Min. Lead length 1.50 inches (38.1 mm) Lead diameter 0.016 to 0.021 inches (0.41 to 0.53 mm) Tag length 0.029 to 0.045 inches (0.74 to 1.14 mm) Tag width 0.028 to 0.034 inches (0.71 to 0.86 mm) -- Steven S. Pietrobon, Small World Communications, 6 First Avenue Payneham South SA 5070, Australia fax +61 8 7117 1416 steven@sworld.com.au http://www.sworld.com.au/