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Bridging Theory in Practice

Bridging Theory in Practice. Transferring Technical Knowledge to Practical Applications. Transistors and Integrated Circuits. Transistors and Integrated Circuits. Transistors and Integrated Circuits. Intended Audience: Engineers with little or no semiconductor background

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Bridging Theory in Practice

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  1. Bridging Theory in Practice Transferring Technical Knowledge to Practical Applications

  2. Transistors andIntegrated Circuits

  3. Transistors and Integrated Circuits

  4. Transistors andIntegrated Circuits Intended Audience: • Engineers with little or no semiconductor background • A basic understanding of electricity is assumed Topics Covered: • Bipolar Junction Transistors (BJTs) • Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) • Integrated Circuits • Moore’s Law Expected Time: • Approximately 90 minutes

  5. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  6. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  7. Bipolar Regions of Operation VBE Active Saturation VBC Cut-Off Inverted Collector IC Device On Device Partly On Base IB IE IE = IC + IB Device Off Device On Upside Down Emitter

  8. Bipolar Regions of Operation Saturation IC IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1 VCE Cut-Off IB = 0 Collector IC Base IB Emitter

  9. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  10. Bipolar Transistors Are “Current Controlled” Devices For a specific bias configuration (VCE), the collector current is determined by the base current Circuits with bipolar transistors are designed to provide the required amount of base current IC VCE Cut-Off IB = 0 Saturation IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1

  11. IC C B IC IB VCE Cut-Off IB = 0 E Bipolar Transistor Gain (b) • In ACTIVE mode, the collector current is almost constant Saturation IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1

  12. IC VCE Cut-Off IB = 0 Bipolar Transistor Gain (b) Saturation • The BJT gain (b) in active mode is defined as: b =IC / IB • Sometimes, the gain is also given as: hFE =IC / IB IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1

  13. At room temperature, β ranges from 240-290 across 3 orders of magnitude Bipolar Transistor Gain (b) • The BJT gain is somewhat independent of the collector current: 1000 800 600 500 β 400 300 25C 200 100 1mA 0.01mA 0.1mA 10mA 100mA Collector Current

  14. Collector Current Base Current Bipolar Transistor Gain (b) • In the ACTIVE mode, fluctuations in base current result in amplified fluctuations in collector current Current time

  15. b b b b b b Bipolar Transistor Gain (b) • In the ACTIVE mode, fluctuations in base current result in amplified fluctuations in collector current b = IC / IB Current b b b time

  16. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  17. Collector IC RIR IR Base IB IF FIF -(IB+IC) = IE Emitter Bipolar Junction Transistor Ebers-Moll Model (1954) Collector IC Base IB Emitter

  18. Bipolar Junction Transistor Performance vs. Temperature As temperature increases, the gain of the BJT increases b about doubles over temperature 1000 700 500 β 300 200 100 1mA 0.01mA 0.1mA 10mA 100mA

  19. Since the gain of the transistor increases with temperature, THERMAL RUN AWAY can occur Bipolar Junction Transistor Performance vs. Temperature • As the temperature increases, the gain increases • As the gain increases, the collector current increases • As the collector current increases, more power is dissipated • As more power is dissipated, the temperature increases • Go back to step 1. • As the temperature increases, the gain increases • As the gain increases, the collector current increases • As the collector current increases, more power is dissipated • As more power is dissipated, the temperature increases • As the temperature increases, the gain increases • As the gain increases, the collector current increases • As the collector current increases, more power is dissipated • As the gain increases, the collector current increases • As the temperature increases, the gain increases • As thermal run away begins, it can move the BJT away from the expected operating bias point • Eventually, if the temperature of the device increases above the maximum rated junction temperature (TJUNCTION,MAX), the bipolar transistor can be damaged or destroyed

  20. Original Ideal Curve Bipolar Junction Transistor Deviations from Ideal Curves Saturation IC IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1 IB = 0 VCE

  21. Saturation Bipolar Junction Transistor Deviations from Ideal Curves • Early Effect – Gain (b) increases with Collector Emitter Voltage IC IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1 IB = 0 VCE

  22. Saturation Bipolar Junction Transistor Deviations from Ideal Curves • Above VCEO, the BJT does not function as expected... IC IB = 5 Active IB = 4 IB = 3 IB = 2 IB = 1 IB = 0 VCE VCEO

  23. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  24. V = IR = 4V VC = 1V IB = (1V – 0.7V) = 10mA IC= β IB =1A 30 IB ~0.7V Bipolar Transistor Biasing 5V 4 Collector 30W Base β = 100 1V Emitter

  25. VC = 1V IC= β IB =1A IB = 10mA ~0.7V Bipolar Transistor Biasing 5V • Operating as an amplifier: 4 Collector 1mVpp 30W Base b = 100 1V Emitter

  26. iB = 1mVpp / 30 = 33App IC= β IB =1A iC = 3.3mA iB ~0.7V Bipolar Transistor Biasing 5V • Operating as an amplifier: 4 vC = 13.3mVpp VC = 1V Collector 1mVpp 30W Base b = 100 IB = 10mA 1V Emitter

  27. Bipolar Transistor Biasing 5V • Operating as an amplifier: 4 Collector 1mVpp 30W Base b = 100 1V Emitter

  28. Bipolar Transistor BiasingWorst Case Analysis 5V • Operating as an amplifier: 4 Collector 1mVpp 30W max = 200 typ = 100 min = 50 Base 1V VBE,max = 0.8V VBE,typ = 0.7V VBE,min = 0.5V Emitter

  29. Bipolar Transistor BiasingWorst Case Analysis Collector Voltage VBE 0.5V 0.7V 0.8V 1.67V ± 6.67mV 3.00V ± 6.67mV 3.67V ± 6.67mV 50 Circuit Fails 1.00V ± 13.3mV 2.33V ± 13.3mV  100 Circuit Fails Circuit Fails Circuit Fails 200

  30. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  31. Sub-Threshold Region VThreshold (VT) MOSFET Two BasicRegions of Operation ID Drain ID Above (Super) Threshold Gate VGS Source

  32. ID VDS = VGS - VT VDS MOSFET Super Threshold Regions of Operation Linear Region Drain VGS = 5V Saturation Region ID VGS = 4V Gate VGS = 3V VGS = 2V VGS = 1V Sub-threshold Region VGS = 0V Source

  33. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  34. ID VDS MOSFETs Are “Voltage Controlled” Devices • For a specific bias configuration (VDS), the drain current is determined by the gate-source voltage • Circuits with MOSFETs are designed to provide the required amount of gate voltage VGS = 5 VGS = 4 VGS = 3 VGS = 2 VGS = 1 VGS = 0

  35. ID VDS MOSFET Transconductance (gm) • The MOSFET gain (b) in active mode is NOT defined as: b = ID / VGS • Rather, we speak of a MOSFET's tranconductance: gm=ID/ VGS VGS = 5 VGS = 4 VGS = 3 VGS = 2 VGS = 1 VGS = 0

  36. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  37. MOSFET Equationsand Models Square Law Model Simple, easy for hand calculations Inaccurate for modern devices Bulk Charge Theory Moderately complex for hand calculations Inaccurate for modern devices Charge Sheet Model Complex Almost as accurate as the exact charge model Exact Charge Model Very complex Very accurate for older and modern devices

  38. MOSFET Square Law Model Subthreshold Region Linear Region Saturation Region G a t e S o u r c e D r a i n ID = 0A W L ID = ( ox / tox ) ( W / L ) [ ( VGS – VT )VDS - VDS2/2 ] ID = ( ox / 2tox )( W / L )(VGS – VT)2

  39. Transistors andIntegrated Circuits • Bipolar Junction Transistors • Regions of Operation • Current Control Device • Equations and Models • Basic Bias Circuit • Metal Oxide Semiconductor Field Effect Transistors • Regions of Operation • Voltage Control Device • Equations and Models • Inverter Circuit • Integrated Circuits • Moore’s Law

  40. n-Channel MOSFET (nMOS)Acting as a Switch Switch is Off VGate = 0V Switch is On VGate = VDrain VDrain = 5V VDrain = 5V IDrain VGate 0V VGate = 5V VSource 0V VSource 0V

  41. p-Channel MOSFET (pMOS)Acting as a Switch Switch is Off VGate = VSource Switch is On VGate = 0V VSource = 5V VSource = 5V IDrain VGate = 5V VGate 0V VDrain 0V VDrain 0V

  42. Complementary MOSFET “CMOS” Inverter 5V In Out 0V

  43. Complementary MOSFET “CMOS” Inverter 5V In = 0V Out 0V

  44. Complementary MOSFET “CMOS” Inverter 5V In = 0V Out With VGate = 0V, a nMOS transistor does not form a channel 0V

  45. Complementary MOSFET “CMOS” Inverter 5V In = 0V Out With VGate = 0V, a nMOS transistor does not form a channel Switch OFF 0V

  46. Complementary MOSFET “CMOS” Inverter 5V With VGate = 0V, a pMOS transistor does form a channel In = 0V Out With VGate = 0V, a nMOS transistor does not form a channel Switch OFF 0V

  47. Complementary MOSFET “CMOS” Inverter 5V With VGate = 0V, a pMOS transistor does form a channel Switch ON In = 0V Out With VGate = 0V, a nMOS transistor does not form a channel Switch OFF 0V

  48. Complementary MOSFET “CMOS” Inverter 5V With VGate = 0V, a pMOS transistor does form a channel Switch ON Current tries to flow In = 0V Out With VGate = 0V, a nMOS transistor does not form a channel Switch OFF 0V

  49. Complementary MOSFET “CMOS” Inverter 5V With VGate = 0V, a pMOS transistor does form a channel Switch ON Current tries to flow In = 0V Out = 5V With VGate = 0V, a nMOS transistor does not form a channel Switch OFF 0V

  50. 5V In = 5V Out 0V Complementary MOSFET “CMOS” Inverter

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