Exercise: Germanium Radio - 慶應義塾大学 徳田研 …kaz/mori_adc_2015_report/...Transistor Amplifiers ! Grounded-emitter transistor amplifier ! Most often-used transistor

アナログ・デジタル電子回路基礎

FUNDAMENTALS OF ANALOG AND DIGITAL CIRCUIT

能動素子 トランジスタの特性

Kazu. TAKASHIO

Exercise: Germanium Radio !  Simulate a germanium radio circuit..

Exercise: Germanium Radio !  Amplitude Modulation (AM)

!  Modulation: Amplitude of carrier wave x Amplitude of modulation wave

!  Amplitude modulation factor: m = (A - B)/(A + B) A: Peak of amplitude envelope curve B: Valley of amplitude envelope curve

!  Input wave A !  Modulation wave: 10kHz (2.5mVp-p)

with 5mV offset voltage !  Carrier wave: 594kHz (NHK 1)

!  Input wave B !  Modulation wave: 20kHz (2.5mVp-p)

with 5mV offset voltage !  Carrier wave: 954kHz (TBS)

Exercise: Germanium Radio !  Tuning circuit (LC parallel resonance circuit) !  At resonance frequency (fr = 1/(2π√(LC))) extremely high impedance..

!  C1 = 276pF -> fr = 594kHz !  C1 for receiving TBS?? !  D1: Wave detection (detector) !  C1: Filtering out the carrier (LPF)

ゲルマニウムダイオード 受信アンテナ

信号電流

レシーバ

同調回路 （並列型）

Tuning Parameters !  Resonance frequency: fr = 1/(2π√(LC))

!  fr = 594kHz，L = 260μH !  C1 ≒ 107pF

Observation of Waveform !  V(am)，V(lc) and V(out)

Transistor !  The greatest invention of the 20th century

!  J. Bardeen, W. Shockley and W. Brattain at AT&T Bell Labs, 1948 !  H. Uchida’s work at NHK STRL was first?.. ignored by GHQ??

!  Commercialized device by TOKYO Tsushin Kogyo (current SONY), 1954 !  The first commercially successful transistor radio (TR-55), 1955

!  Two uses (applications..) !  As an amplifier

!  Current gain !  Voltage gain !  Power gain

!  As a switch !  Logic gates

Transistor !  Junction transistor

!  Three regions of doped semiconductors !  PNP type !  NPN type

!  As a current amplifier !  The smaller current in the base acts as a "valve", controlling the larger current from collector to emitter..

Types of Transistors !  Bipolar transistor >> Current driven

!  NPN transistor !  PNP transistor

!  Unipolar transistor (field-effect transistor) >> Voltage driven !  Junction field-effect transistor (J-FET)

!  N channel J-FET !  P channel J-FET

!  Metal‒oxide‒semiconductor field-effect transistor (MOS-FET) !  N channel MOS-FET !  P channel MOS-FET

Transistor: Operations !  Switching

!  As a high-speed relay.. !  Mechanical relay < 10Hz !  Transistor >> 100MHz

!  High-voltage / high-current switching.. !  An output current of a microcomputer or a gate IC is about 20mA..

!  A transistor or a MOS-FET attached to a microcomputer’s I/O port enables to drive a relay, solenoid, motor or super luminosity LED, or to control a power source..

!  Amplification !  Operate a transistor in intermediate state between ON and OFF, and have it generating a large signal similar to an input signal..

Exercise in the Kickoff Class !  ex: Switching operation of a NPN Transistor

LTspice: Simulation !  Run simulation.. : [Run] icon !  Select a signal.. : VIN／VOUT／IB（Base current）

!  Voltage Probe

!  Current Probe

Switching Operation

PMOSトランジスタのスイッチング動作

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!  MOS (Metal Oxide Semiconductor) transistor !  3 terminals: Source (S) / Drain (D) / Gate (G) !  Field-effect transistor (FET)

!  Logic gates

!  NOT !  NAND !  NOR

Logical Operation (Operator..) Input Output A out 0 1 1 0

Input Output A B Y 0 0 0 0 1 1 1 0 1 1 1 1

Logic Operation

Boolean Expression Circuit Symbol (MIL)

NOT A OR A + B AND A・B XOR A + B NOR A + B NAND A・B

Logical Operation (Operator..) Input Output

A B Y 0 0 0 0 1 0 1 0 0 1 1 1

Logic Operation

Boolean Expression Circuit Symbol (MIL)

NOT A OR A + B AND A・B XOR A + B NOR A + B NAND A・B

Input Output A B Y 0 0 0 0 1 1 1 0 1 1 1 0

Logical Operation (Operator..) Input Output

A B Y 0 0 1 0 1 0 1 0 0 1 1 0

Logic Operation

Boolean Expression Circuit Symbol (MIL)

NOT A OR A + B AND A・B XOR A + B NOR A + B NAND A・B

Input Output A B Y 0 0 1 0 1 1 1 0 1 1 1 0

Transistor Amplifiers !  Grounded-emitter transistor amplifier

!  Most often-used transistor amplifier circuit !  Base input, collector output (inverted phase) !  Good power gain, but not so good frequency characteristics !  Fixed bias

エミッタ接地 ベース接地 コレクタ接地

負荷抵抗

直流削除用 直流 削除用

固定 バイアス用 電流帰還用

バイアス抵抗

バイパス コンデンサ

直流削除用

電流制御用 抵抗（負荷）

負荷抵抗

負荷抵抗 固定 バイアス用

直流削除用 直流 削除用

Transistor Amplifiers !  Grounded-base transistor amplifier

!  Emitter input, collector output !  High power gain, 0dB current gain !  Two powered bias for current control on emitter.. !  Good frequency characteristics

エミッタ接地 ベース接地 コレクタ接地

負荷抵抗

直流削除用 直流 削除用

固定 バイアス用 電流帰還用

バイアス抵抗

バイパス コンデンサ

直流削除用

電流制御用 抵抗（負荷）

負荷抵抗

負荷抵抗 固定 バイアス用

直流削除用 直流 削除用

Transistor Amplifiers !  Grounded-collector transistor amplifier (emitter follower)

!  Base input, emitter output !  High current gain, 0dB voltage gain !  Good high-frequency property in over 100MHz.. !  Low output impedance

エミッタ接地 ベース接地 コレクタ接地

負荷抵抗

直流削除用 直流 削除用

固定 バイアス用 電流帰還用

バイアス抵抗

バイパス コンデンサ

直流削除用

電流制御用抵抗（負荷）

負荷抵抗

負荷抵抗 固定 バイアス用

直流削除用 直流 削除用

Transistor: Basic Characteristics !  DC amplification factor: hFE = IC / IB !  Base-emitter voltage: VBE = 0.6V ～ 0.7V (0.65V in normal) !  IC - VCE characteristics (static characteristics)

電源電圧

電源電圧／負荷抵抗

動作点

動作線

歪みが生じる

Grounded-Emitter Transistor Amplifier

VE

IE

IC

VC

VBE

VB

IB

Ibias

!  Parameters !  Fixed bias for VB !  Current feedback bias with RE

!  Calculation of resistance values !  Decide IC from the circuit spec.

>> ex. IC = 1mA !  Usually VE needs 0.5 - 2V for absorbing

the effect of temperature change.. >> ex. VE = 1.5V

!  IB is quite small IC ≒ IE >> RE = VE / IC = 1.5kΩ

!  VB = VE + VBE VBE = 0.65V >> VB = 1.5 + 0.65 = 2.15V

Grounded-Emitter Transistor Amplifier

VE

IE

IC

VC

VBE

VB

IB

Ibias

!  Calculation of resistance values (contd.) !  Ibias should be define 10 times of IB (hFE of most transistors are

100 - 300, thus 1/10 - 1/30 of IC is appropriate).. >> ex. Ibias = 143μA

!  Ibias >> IB RB2 = VB / Ibias >> RB2 = 2.15 / 140 ≒ 15kΩ >> RB1 = ... = 68kΩ

!  Bypass capacitor CE !  Increase AC gain while maintaining

the temperature stability by RE.. !  Distortion increases in

proportion to the gain.. !  Gain depression in

low-frequency area 　 >> ex. CE = 100μF

Grounded-Emitter Transistor Amplifier

VE

IE

IC

VC

VBE

VB

IB

Ibias

!  Operating point of VC !  In case of no signal on CE

VC = VCC - RC IC !  RC = 4.7kΩ >> VC = 12 - 4.7k × 1m = 7.3V

!  Voltage gain on AC amplification !  Inner resistances: rb，re，rc !  ZCE is quite small for AC signal..

vb = rb ib + re ie !  Replace “AC current gain hfe” as β..

ie = ib + βib = (1 + β) ib !  Input impedance Zie:

Zie = vb / ib = rb + (1 + β) re !  rb of Small signal transistor:

50 - 500Ω When the β is sufficiently-large Zie ≒ (1 + β) re ≒ βre

Grounded-Emitter Transistor Amplifier

VE

IE

IC

VC

VBE

VB

IB

Ibias

!  Voltage gain on AC amplification (contd.) !  Voltage gain: Av = vout / vb !  vout = RC β ib and ib = vb / Zie

>> Av = vout / vb = βRC / (βre) = RC / re !  Emitter inner resistance: re

!  Resistance in forward direction diode !  Determined by physical property

>> re ≒ (26 / IE [mA]) Ω

!  Without CE !  Replace re with re + RE

>> Av = RC / (re + RE) ≒ RC / RE

Simulation !  Transistor 2N3904, collector current 1mA

Exercise: Circuit Evaluation !  Observe DC operation points in no signal case..

!  DC bias point simulation !  In [LTspice directive] > [Analysis Cmd.] > [DC Bias Point] tab,

define “.op” and place on the schematic.. !  Operation points are saved in a log file (xxx.log).. !  Compare observed voltage values with expected values..

!  Measure voltage gain from amplified waveform.. !  Transient analysis mode “.tran 10m” !  Measure amplitude of V(vout) and calculate gain..

!  Observe distortion of waveform !  Transient analysis mode “.tran 100m” !  In waveform window, [View] > [FFT] !  Compare the level of basic wave and second order harmonics [dB].

Exercise: Circuit Evaluation !  Observe frequency characteristics of voltage gain..

!  AC analysis mode “.ac dec 100 1 100MEG” !  Frequency characteristics of output voltage

!  Display in dB (dBV) !  Display voltage gain with [Add Trace] command..

!  Output voltage / input voltage !  R3 (after VIN): Inner resistance of power source

!  Evaluate cutoff frequencies in low-frequency area and high-frequency area.. !  Cutoff frequency: -3dB (1/√2) point

!  Bypass condenser and frequency characteristics !  Replace value of C2 with “{Cbp}”.. !  Parametric sweep analysis “.step param Cbp 20u 200u 20u” !  Observe the behavior of cutoff frequency..

Exercise: Circuit Evaluation !  Question

!  Report the result of simulations..

!  Submit to SFC-SFS !  Deadline: 23rd Oct. 23:59