Tektronix G 20 MHz Wide-Band Differential Amplifier Plug-In (1969)

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Quick Specifications / Photos
Detailed Specifications
Operating Instructions
Misc. Part Numbers

Samples of e-Bay Prices
Tektronix Catalog CostLow BidHigh Bidaverage
$205 (1969)    
no bids (asked $9.99) 12/22/05 #7573284282 sunnking (untested)
$9.99 1/13/06 #7579130567 sunnking (1 bid) (untested)
$37.50 (+$17 ship) 11/4/07 #330182933941 2100aweek (7 bids $9.99 start) (in original unopened box)
$19.99 (+~$11 ship) 5/22/08 #250248431882 friends_of_marcus (1 bid) (untested)
$19.38 (+$14 ship) 6/10/09 #270402504798 angielazarit (2 bids $0.99 start) (missing a few tubes)

  • Bandwidth - Up to 20 MHz
  • Risetime - down to .015μsec
  • .05 V/CM to 20 V/CM


    Tektronix Type G Plug-In.
    The Type G Unit is suited to work requiring differential input and high rejection ratio. It has wide band pass and good transient response. It may be used with Tektronix Type 530, 540, 550, and 580 series oscilloscopes. For use with Type 580 Series Oscilloscopes a Type 81 or Type 81A Plug-In Adapter must be used. The differential input permits cancellation of unwanted or interfering signals.

    The Plug-In Unit was first known as Type 53G and then changed to Type 53/54G and finally to Type G Plug-In unit.

    Type G Specifications
    Instrument Used WithPassband *Transient Response (10% to 90%)
    541, 541A, 543, 545, 545A, 555 and 580-Series using 81 or 81A adapter.DC to 20 MHz.018 μsec
    531, 535, 536DC to 10 MHz.035 μsec
    532DC to 5 MHz.07 μsec
    531A,533, 535ADC to 14 MHz.025 μsec
    551DC to 18MHz.02 μsec
    * Down not more than 3 db at indicated limits.

    Plug-In Amplifier

    0.015 μsec

    Deflection Factor

    Calibrated - 0.05 v/cm to 20 v/cm.
    Continuously Variable - .05 v/cm to 20 v/cm.

    Step Attenuator :

    Nine positions, calibrated, from .05 v/cm to 20 v/cm, accurate within 4% when set on any one step. Independent step attenuator in each input with 80 db isolation. This permits mixing of signals of wide amplitude difference.

    Maximum Allowable Compined DC and Peak AC

    Input Voltage - 600 V

    Differential Input

    100-to-1 rejection ratio at full gain for any in-phase signal within the pass band of the instrument and better than 300-to-1 rejection ratio for 60 Hz; maximum amplitude handling capability, 2 volts, peak-to-peak, between the input grids of the input amplifier tubes.

    Input Impedance - 1 megohm, 47 pf.

    With P410 Probe - 10 megohms, 11 pf.

    With P510 Probe - 10 megohms, 14 pf.

    With P6000 Probe - 10 megohms, 14.5 pf.

    Separate signal inputs to the preamplifier by way of the INPUT SELECTOR switch.
    VOLTS/CMTwo 9-position switches, one in each input circuit, to select the desired deflection factor.
    INPUT SELECTOR SWITCHSix-position switch, to select either input separately or the two inputs differentially, with either ac or dc coupling.
    VARIABLE (volts/cm)Control to vary the gain over a range of about 2 ½ to 1.
    VERTICAL POSITIONControl to position the trace vertically.
    GAIN ADJ. (S/N 1917-up only)Screwdriver control to adjust the basic gain of the amplifier.
    DC BALScrewdriver adjustment to set the dc voltage across the VARIABLE VOLTS/CM control to zero so the trace does not shift when the gain is varied.
    DIFF. BAL.Screwdriver control to provide a fine differential adjustment of the input amplifier gain for the maximum rejection of the common-mode signal.

    above excerpts from Tektronix Type B Plug-In Instruction Manual

    Input Connections

    Two cables can be connected to the preamp at once.
    Either of the two signal inputs can be used independently by turning the INPUT SELECTOR switch to A or -B and connecting the signal to the corresponding input connector. The signal will be inverted when connected to INPUT B.
    The DC and AC positions of this switch differ only in that, in the AC positions, a capacitor is inserted in series with the input to remove the dc component of the signal. In the AC position, the capacitor that is inserted limits low frequency response to 3 db down at 2 Hz.
    When the INPUT SELECTOR switch is in either position marked A-B, both inputs are connected to the amplifier through individual compensated attenuators. The signal presented to the oscilloscope amplifier will be the difference between these two signals after attenuation. This makes it possible to balance out a large signal with a relatively small one, or vice versa, by appropriate selection of deflection factors.

    Differential Input

    The differential input makes possible the application of balanced signals to the G preamp. The best rejection ratio for common mode signals is obtained in the unattenuated (maximum gain) position. When a balanced input is required, be sure both VOLTS/CM switches are on the same deflection factor position.
    Sometimes it is desirable to use different deflection factors on the two inputs. You can buck out 60 Hz hum in a signal being viewed by applying a properly phased 60 Hz signal to the unused input. If variable attenuation is necessary, this must be done externally. You can buck out up to 600 volts dc by connecting a battery to the unused input. You should not exceed 4 volts input when in the maximum gain position or at the input grid after attenuation.

    Differential-Balance Adjustment

    The DIFF.BAL. control balances the amplifiers so that when the same signal is connected to both inputs, the output signal is reduced to a minimum. To adjust the DIFF.BAL. control, connect a two-volt signal from the calibrator to both INPUT A and INPUT B without the probes connected. Set the INPUT SELECTOR switch to A-B. Set both VOLTS/CM controls to .05. Adjust the DIFF.BAL. control to obtain a straight line on the scren.

    The rejection ratio for a balanced input is reduced when the probes are used or when the VOLTS/CM switches are in positions other than for maximum deflection factor. This is caused by the one-percent tolerances of the resistors in the attenuators and input circuits. The rejection ratio can be improved for lower deflection factors by setting the DIFF.BAL. control for the specific position on fht VOLTS/CM switch that is to be used. Connect the calibrator to both inputs simultaneously with a convenient calibrator output voltage for the deflection factor to be used. Set the INPUT SELECTOR switch on A-B, and adjust the DIFF. BAL. control for minimum signal. It should be possible to pass through a minimum with the DIFF.BAL. control.

    Gain Adjustment

    Aging of tubes will affect the gain of the plug-in unit. After the plug-in unit has been in use for a period of time, the gain adjustment should be checked. Display a cliabrator waveform of .2 volts peak-to-peak with the VOLTS/CM switch in the .05 position of Input A. Adjust the GAIN ADJ. control until the displayed waveform is four graticule divisions in amplitude. Be sure the VARIABLE control is turned clockwise to the CALIBRATED position before making this adjustment.

    MISC PART NUMBERS (s/n 1001 up)
    366-0117-00Knob, Charcoal VOLTS/CM "A"
    366-0117-00Knob, Charcoal VERTICAL POSITION
    366-0117-00Knob, Charcoal VOLTS/CM "B"
    366-0113-00Knob, Charcoal INPUT SELECTOR
    366-0045-00Knob, Black VARIABLE VOLTS/CM
    SW3017260-167Switch, Rotary, INPUT SEL.
    SW3347260-166Switch, Rotary, VOLTS/CM A
    SW4347260-166Switch, Rotary, VOLTS/CM B
    R3717311-285Res, Var, WW 880 ohm