Integrated circuits

What it is

An integrated circuit (IC, or chip) is a complete circuit, with its transistors, diodes, resistors and capacitors, built on one tiny slice of silicon and sealed in a package with pins. Putting everything on one die makes circuits smaller, cheaper, more reliable and better matched than the same circuit built from separate parts. An IC may hold a handful of transistors or billions.

Kinds of IC

Kind	What it does	Examples you meet in radios
Analog (linear)	works on smoothly varying signals	op-amps, audio amplifiers, voltage regulators, comparators, 555 timers
Digital	works on ones and zeros	gates, counters, memory
Mixed-signal	bridges the two	ADCs and DACs, PLL synthesizers
RF / MMIC	a whole microwave amplifier, mixer or switch on one chip	gain blocks and preamplifiers, typically with 50 Ω input and output
Programmable	a processor or logic array you program	microcontrollers, DSPs, FPGAs

An FPGA is not programmed with instructions but configured, using a hardware description language (HDL), to wire up its own gates into the circuit you describe.

Digital families

Digital chips are built in logic families. TTL (bipolar transistors) is older and uses more power. CMOS (MOSFETs) uses very little power when idle, and its input switches at about half the supply voltage, which gives it good noise immunity. BiCMOS combines the two: the high input impedance of CMOS with the strong output drive of bipolar transistors.

Packages

In practice

• Read the datasheet: it gives the pinout, the supply-voltage range and the absolute maximum ratings. Exceeding a maximum, even briefly, can destroy a chip.
• Bypass the supply: put a small capacitor (commonly about 0.1 µF) across the supply pins, close to the chip. It supplies the brief current spikes digital chips draw.
• Do not leave inputs floating: an unconnected CMOS input can drift and make the output erratic. Tie it high or low, or use a pull-up or pull-down resistor.
• Match logic levels: a 5 V output can overdrive a 3.3 V-only input. Check both chips' ratings or use a level shifter.
• Static: CMOS chips are static-sensitive just as MOSFETs are. Handle them with care.
• Noise: the fast edges of digital chips radiate. A microcontroller or switching regulator can be a source of radio interference; see RFI and EMI overview.

Related

• Operational amplifiersThe building block of gain, filters and comparators.
• Logic gatesAND, OR, NOT, NAND, NOR and XOR.
• MicrocontrollersArduino, Pico and friends in the ham shack.
• ADCs and DACsConverting between analog voltages and numbers.
• PLLs and frequency synthesizersLocking a variable oscillator to a stable reference.
• FETs and MOSFETsVoltage-controlled devices for switching and RF.