2205

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The Tektronix 2205 is a 20 MHz dual-trace analog oscilloscope introduced in 1989. There is a also a 40 MHz version, the 2205-40.

Specifications

Bandwidth 20 MHz
CRT 1.8 kV cathode voltage, no post-deflection acceleration
Weight 6.2 kg (13.7 lb)
Power max. 40 W

please expand

Prices

1990: $695 ($1440 in 2021 dollars)

Internals

Each of the two inputs first goes through attenuators, then discrete dual-JFET source-follower buffer stage, then an Intersil CA3102 differential amplifier chip to provide some gain and convert from single-ended to a differential signal.

The vertical output amplifier driving the CRT is discrete and has an interesting design that conserves power (and minimizes heat). When the output is slewing at low rates, the output transistors have a constant, relatively low current passing through them. At higher slew rates, to provide enough current to charge and discharge the parasitic and CRT plate capacitances, the output stage operates in more of a push-pull mode.

The 2205 has a switch-mode power supply that produces low voltage and CRT voltages using transformer T901, which operates at about 60 kHz. Interestingly, there is a also a mains-frequency step-down and isolation transformer (T901) in the power path before the SMPS.

Pictures