1945 — Current Regulator Tube

The 1945 is a current regulator and resistance tube, also referred to as a tube de résistance, Widerstandsröhre, régulateur de courant, or Stromregler. It is designed to maintain a stable current of approximately 0.275 A across a control voltage range of 80 V to 120 V.

Physical Specifications and Base Configurations

The 1945 is constructed with a tubular glass bulb envelope. Its physical dimensions include a maximum diameter of 38 mm and a maximum overall height of 115 mm (with some specifications noting this length excludes the pins).

Depending on the manufacturer and production variant, the 1945 is available with two distinct base configurations:

9-Pin "P." Type Base

In this configuration, the tube features a 9-pin "P." type base. The pins are arranged as follows:

• Pins 1 through 7: Auxiliary pins.
• 'f' Pins: Two separate filament pins between which the active resistance/regulating element is connected.

8-Pin Octal Base

Alternatively, the tube is available with a standard 8-pin octal base configuration. The pinout for this variant is defined as:

• Pins 1 and 8: Connected to the filament / regulating element (f).
• Pins 2, 3, 4, 5, 6, and 7: Interconnected internally.

Electrical Characteristics and Regulation Performance

The primary function of the 1945 is current regulation. It operates over a specified voltage window, absorbing voltage fluctuations to maintain a relatively steady current through its series-connected load.

The tube-to-tube current tolerances indicate that at the nominal operating point, individual specimens of the 1945 will exhibit a regulated current within a tight window of 263 mA to 283 mA.

Characteristic Curve Analysis

The current-voltage ($I/V$) characteristic curve of the 1945 illustrates its behavior across the regulating range of 80 V to 120 V. The current-voltage characteristic curve is nearly linear and shows a steadily rising current over this range:

• At 80 V: The current is approximately 0.225 A.
• At 100 V (Mean Voltage): The current is approximately 0.27 A to 0.275 A.
• At 120 V: The current is approximately 0.32 A to 0.325 A.

This nearly linear relationship demonstrates that while the tube acts as a current-limiting resistance element, the current does rise gradually as the voltage across the device increases from the lower to the upper limit of its control range.

Technical Summary

The 1945 is a specialized current regulator tube designed to operate with a nominal current of 0.275 A over an active voltage range of 80 V to 120 V. Housed in a 38 mm diameter tubular glass bulb with a height of 115 mm, it is found with either a 9-pin "P." type base or an 8-pin octal base. Its electrical characteristics are defined by a mean operating voltage of 100 V and a controlled current tolerance between 263 mA and 283 mA, making it a reliable series resistance element for stabilizing electrical circuits.