2205

The Tektronix 2205 is a 20MHz dual-trace analog oscilloscope.

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 a T901, which operates at about 60kHz. Interestingly, there is a also a mains-frequency isolation transformer (T901) in the power path before the SMPS.

The 2205 has 1.8kV on the cathode and does not use post-deflection acceleration of the CRT electron beam.

The 2205 weighs 13.7 pounds and consumes a maximum of 40 watts.

• Tektronix 2205 Service Manual (PDF)
• Tektronix 2205 Operators Manual (PDF)