Comparison of MCA and Discrete Failure Rates Summary MIL-HDBK-217F is used to compare the reliability of a discrete vs an MCA design. The system is assumed to consist of 12 2N2222A transistors, operating in an Airborne Inhabited Fighter environment. Discrete System: λ p = 0.81 failures/106 operating hours MCA System: λ p = 0.32 failures/106 operating hours Discrete Calculation Transistor, Low Frequency, Bipolar (MIL-HDBK-217F Section 6.3) Transistor failure rate λ p = λ bπ T π Aπ R π S π Qπ E Base failure rate λ b = 0.00074 Temperature factor π T = 2.1 (Assume Tj = Tcase = 60°C) Application factor π A = 1.5 (Linear Amplification) Power Rating Factor π R = 1.0 (Power = 1W) Voltage Stress Factor π S = 1.0 (VCE = VCEO, Vs = 1.0) Quality factor Π Q = 1.0 (JANTX) Environmental factor Π E = 29 (Aircraft Inhabited Fighter) Þ λ p = 0.00074 * 2.1 * 1.5 * 1.0 * 1.0 * 1.0 * 29 = 0.06760 Number of 2N2222A die N = 12 Þ Nλ p = 12 * 0.06760 = 0.8112 MCA Calculation Transistor, Low Frequency, Bipolar (MIL-HDBK-217F Section 6.3) Transistor failure rate λ p = λ bπ T π Aπ R π Sπ Qπ E Base failure rate λb = 0.00074 Temperature factor π T = 2.1 (Assume Tj = Tcase = 60°C) Application factor π A = 1.5 (Linear Amplification) Power Rating Factor π R = 1.0 (Assume Power = 1W) Voltage Stress Factor π S = 1.0 (Assume VCE = VCEO, Vs = 1.0) Quality factor Π Q = 1 (Hybrid) Environmental factor Π E = 1 (Hybrid) Þ λ p = 0.00074 * 2.1 * 1.5 * 1.0 * 1.0 * 1 * 1 = 0.002331 Dr D.Hinchley 12 Jul 2000 www.semelab.com Tel +44 (0)1455 556565 Page 1 of 2 Hybrid (MIL-HDBK-217F Section 5.5) Hybrid failure rate λ p = [NC λC ](1 + 0.2π E )π F π Qπ L Number of 2N2222A die NC = 12 2N2222A failure rate λC = 0.002331 Environmental factor π E = 5.0 (Airborne Inhabited Fighter) Circuit function factor π F = 5.8 (Linear, f < 10MHz)) Quality factor Π Q = 1.0 (Class B) Learning factor Π L = 1.0 (> 2yrs in production) Þ λ p = [12 * 0.002331]* ( 1 + 0.2 * 5.0 ) * 5.8 * 1.0 * 1.0 = 0.3245 Dr D.Hinchley 12 Jul 2000 www.semelab.com Tel +44 (0)1455 556565 Page 2 of 2