Black Box Electronics
An Introduction to Applied Electronics for Physicists
1. From Zero to BJTs in 60 Minutes
University of Toronto
Quantum Optics Group
Alan Stummer, Research Lab Technologist
Scope of Talk
• Intended for anyone working in physics, preferably at the UofT.
• Provides enough of a background to know what is required in the
research lab, but not necessarily to design it.
• Covers the practical implementation of electronics used in research.
• Covers common components and basic circuits.
• Concepts, not equations.
• No tests! No reports! No homework!
• Does not cover basics such as Ohm’s law, the less common
components or obscure circuits.
Digital
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Analog (RF)
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About 1/4 of engineers
Intuitive, more of an art
Continuum of signals
Transistors, resistors,
capacitors, small ICs
Interface (grey area)
• ADC (Analog to Digital Converter)
• DAC (Digital to Analog Converter)
About 3/4 of engineers
Logical, rational, analytical
Two signal levels only
FPGAs, microprocessors,
ASICs.
• Fields: Industrial, military, consumer commodities (inc computers).
• Please, electronics is not electrical!
(SI) Units
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Voltage:
V
Current:
A
Resistance: Ω
Frequency:
Hz (ω almost always shown as 2πf)
Power:
W
Temperature: °C
Errors as ±%, error bars not used.
The !@#$% “dB”, a throwback to slide rules
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Any ratio: dB
Power: dBm (dBm = 10 Log10P/1mW)
Voltage (relative to 1V): dBv (dBv = 20 Log10V/1V)
Relative to anything: e.g. -3dBc is half power relative to a carrier
Standards & Trends
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Lower and lower operating voltages: supplies of +3.3V down to +0.9V.
Lower and lower power: battery power, standby modes, critical design.
Smaller IC feature size: 90nm common, going to 65nm in 2006.
Smaller ICs: 0.25mm connection pitch, no “pins”.
Faster, higher bandwidth: GHz communications, GHz data rates.
All SMT (surface mount): through-hole relegated to hobbyists.
But still the generic analog IC eludes us, the FPAA (Field Programmable
Analog Array) is the analog holy grail. Attempts have been made, they were
fast but accuracy was needed, they were accurate but speed and power
were needed, they were high power but efficiency and accuracy were
needed, etc.. Maybe next decade?
Data Sheets
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Look for sample or test circuits – very reliable!
Parameters given in minimum, typical, maximum and absolute maximum.
Never exceed abs max, even for 1aS, can cause latent damage.
Specs are usually conservative, [almost] always true.
May have specs for various conditions (voltage, temperature, etc).
Trend now away from Greek, towards more readable descriptions
(e.g. β now hFE)
Conservative Data
Randomly selected, this is from the data sheet for Analog Devices’
AD8571 (and similar) precision op amp, input offset distribution of about
900 units at a supply voltage of 2.7V. Input offset voltage is typically
±1μV, ±5μV maximum. 89% are within typ range.
Supplies
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Use one low voltage positive supply unless you have a good excuse.
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Most common supplies are +5V, +3.3V, +2.7V and lower.
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Reduce power consumption.
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Fuse or limit at 125-200% of maximum current.
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Bypass at every IC with 0.1μF (ceramic) minimum.
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With multiple supplies, ensure sequencing on and off.
Common Components
PASSIVE
ACTIVE
INTEGRATED
Resistor
Capacitor
Inductor
Diode
Transistor
BJT
MOSFET
IGBT
Thyrister
SCR
Triac
Linear
Digital
Loose logic
FPGA et al
Microprocessor
Mechanical
Switch
Connector
Relay
Resistors
• Limited in power, voltage and current.
• Appear inductive at high frequency.
• Range typical from 1Ω to 10MΩ (extreme 1mΩ to 10GΩ).
• Initial tolerance typically ±1% but can go cheap with ±5%.
• Resistance varies with temperature, typically ±50PPM/° (5e-5 /°).
• Prefer values 10X, e.g. 100Ω, 100K.
• 1% values (in 2.43% steps): 100, 102, 105, 107, 110, 113, 115, 118, 121, 124, 127,
130, 133, 137, 140, 143, 147, 150, 154, 158, 162, 165, 169, 174, 178, 182, 187, 191,
196, 200, 205, 210, 215, 221, 226, 232, 237, 243, 249, 255, 261, 267, 274, 280, 287,
294, 301, 309, 316, 324, 332, 340, 348, 357, 365, 374, 383, 392, 402, 412, 422, 432,
442, 453, 464, 475, 487, 499, 511, 523, 536, 549, 562, 576, 590, 604, 619, 634, 649,
665, 681, 698, 715, 732, 750, 768, 787, 806, 825, 845, 866, 887, 909, 931, 953, 976
Capacitors
• AC: Reactance (Xc) α 1 / f
• DC: RC is asymptotic, acts like a battery.
• Limited in voltage, current.
• Appear inductive at high frequency.
• ESR (Equivalent Series Resistance) might dominate.
• Capacitance varies with temperature (typically ±50PPM/°).
• Initial tolerance typically 5% (polarized maybe +80% -20%)
• Prefer values 10X, e.g. 1μF, 10pF.
• Range typical from 1pF to 1000μF, extreme 0.05pF to 3000F (17 decades!).
• Typical 5% values: 10, 12, 15, 18, 22, 27, 33, 47, 56, 68, 82.
Inductors &
Transformers
• Not common components (except for RF and power supplies).
• Inductors limited in current (becomes resistive as it saturates).
• Limited in frequency (become capacitive at high frequency).
• Transformers almost exclusively for power supplies.
Switches and Relays
• Switches are crude electro-mechanical devices that connect or
seperate pieces of metal, controlled by a lever or knob.
• Relays are crude electro-mechanical devices that connect or
seperate pieces of metal, controlled by an electromagnet.
• Contacts are rated for current and voltage (due to oxidation, DC is
usually rated lower).
• Available in single or mutiple contacts.
• Relay contacts are “NO” (normally open) and NC (normally closed).
• Limited in frequency, except for specialized relays.
• Relay coils “pull in” at rated coil voltage and current.
• Switches common for power and signalling.
• Relays not common components, often used for motors.
Diodes
• Common flavours: signal/rectifier, LED, photodiode, Zener.
• Most are silicon, have Vf ~0.7V forward voltage drop (LEDs 1.5V).
• Temperature sensitive, ΔVf = -2.5mV / °.
• Limited in forward current (If) and reverse voltage (Vr).
• Limited frequency range, capacitance dominates at high frequency.
• Select for current, voltage and speed.
• Use common components: 1N4004 (1A, 400V), 1N4148 (signal).
• LEDs typically operate at If = 1-10mA, laser diodes up to >>1A.
• Laser diodes have lasing threshold, incoherent below.
Sample Diode Specs
A fast 500mA, 20V Schottky diode from Panasonic (Digikey.ca).
http://www.semicon.panasonic.co.jp/ds/eng/SKH00039BED.pdf
Forward Voltage
Reverse Leakage
BJTs
(Bipolar Junction Transistors)
• Has current gain (hFE): Current allowed through collector to emitter is
proportional to current through base to emitter.
• Operate in active region (analog), or saturation or cutoff (digital).
• Most are NPN and silicon, have VBE ~0.7V.
• Limited in collector current IC, voltage VCE and power PD.
• Significant saturation VCE(sat).
• Limited frequency range, capacitance dominates at high frequency.
• Select for current, voltage and speed.
• Typical voltage VCE range 10V to 200V, extreme to 1.5KV.
• Typical current IC range 100mA to 10A, extreme 10mA to 100A.
Sample BJT Specs
A General purpose 500mA, 80V Schottky diode from OnSemi (Digikey.ca).
http://www.onsemi.com/pub/Collateral/MMBTA05LT1-D.PDF
Saturation Region
Dependance of hFE
Ω The End Ω
Next:
2. Analog Electronics
3. Digital Electronics
4. Sample Circuits
5. Spice simulations
Then: More in depth on anything? Suggestions?