150C4 — Gas-Filled Voltage Stabilising Tube
A cold-cathode, gas-filled voltage stabiliser designed to provide a constant 150 V output over a wide range of operating currents.
Overview
The 150C4 is a gas-filled voltage stabilising tube engineered to maintain a stable direct voltage of approximately 150 V. It operates over a cathode current range of 5.0 to 30 mA, offering a nominal regulation voltage of 3 V. The tube is designed for reliable voltage regulation in electronic equipment, maintaining its performance characteristics both initially and throughout its operating life.
Construction, Physical Dimensions, and Base Pinout
The 150C4 is constructed in a compact glass envelope utilizing a miniature B7G seven-pin base. The physical dimensions of the tube are specified as follows:
- Maximum overall height: 67.5 mm
- Maximum seated height: 60.5 mm
- Maximum bulb diameter: 19 mm
The B7G base connections provide multiple pins for the anode and cathode electrodes, which can be utilized for circuit strapping or safety interlocking. The pinout configuration, viewed from the bottom of the base, is as follows:
The internal connections (pins 3 and 6) must not be used for external circuit connections other than those specified by the equipment design guidelines.
Ignition and Maintaining Characteristics
To initiate conduction, the voltage applied to the 150C4 must exceed its ignition threshold. The minimum voltage necessary for ignition is highly dependent on the presence of ambient light:
- In some ambient light: A minimum of 185 V is required.
- In complete darkness: A minimum of 225 V is required.
The nominal ignition delay time is 10 seconds. The dark ignition delay time is statistically distributed; the probability of the tube igniting within a given timeframe increases as the applied supply voltage is increased.
Once ignited, the tube exhibits a stable maintaining (or burning) voltage. The maintaining voltage varies slightly depending on the operating current and the age of the tube:
- Initial maintaining voltage (at 30 mA): 156 V to 158 V maximum.
- Initial maintaining voltage (at 5.0 mA): 142 V to 143 V minimum.
- Maintaining voltage over life (at 30 mA): 156 V to 161 V maximum.
- Maintaining voltage over life (at 5.0 mA): 139 V minimum.
Regulation and Life Performance
The regulation voltage represents the change in maintaining voltage when the cathode current is varied across its full operating range of 5.0 to 30 mA.
- Initial regulation voltage: Typically 3.0 V, with a maximum limit of 5.0 V.
- Regulation voltage over life: Typically 3.0 V, with a maximum limit of 8.0 V.
The long-term stability of the maintaining voltage depends on the operating current:
- Continuous operation at 30 mA: Over 1,000 hours of life at room temperature, the maximum variation in maintaining voltage ranges from +1.5% to -5%, with an average variation of ±1%.
- Operation at an average current of 17.5 mA: Over 1,000 hours of life, the typical variation in burning voltage is 1.0%, with a maximum variation of 3.0%.
Absolute Maximum Ratings
To ensure reliable operation and prevent premature failure, the 150C4 must be operated within its absolute maximum ratings:
The maximum surge current of 75 mA is a transient rating and must be restricted for long tube life to approximately 30 seconds in each 8 hours of use.
Technical Summary
The 150C4 is a B7G-based, gas-filled voltage stabilising tube designed to maintain a stable 150 V reference. It supports a continuous cathode current range of 5.0 to 30 mA, with a typical regulation voltage of 3.0 V. The tube requires an ignition voltage of at least 185 V in ambient light and up to 225 V in complete darkness. With its robust thermal ratings and multiple electrode pin connections, the 150C4 provides dependable voltage regulation in professional and industrial electronic applications.
