150B2 — Voltage Stabiliser Tube

A cold-cathode, gas-filled voltage stabiliser and reference level tube designed to establish and maintain a stable 150 V DC output across a wide range of operating conditions.

Overview

The 150B2 (also designated as 150 B 2) is a miniature, gas-filled stabilising tube designed for voltage regulation and reference applications. It provides a nominal maintaining voltage of 150 V over a recommended cathode current range of 5.0 to 15 mA. Manufactured by companies such as Mullard and Philips, the tube is engineered to deliver high stability, low temperature drift, and reliable ignition characteristics throughout its operating life.

Construction, Base, and Pinout

The 150B2 is constructed in a compact glass envelope utilizing a standard Miniature 7-pin (B7G) base. Its physical dimensions are highly standardized, though minor variations exist across manufacturing specifications:

• Maximum Bulb Diameter: 19 mm
• Maximum Seated Height: 47.5 mm to 48 mm
• Maximum Overall Height: 54 mm to 54.5 mm

Pin Connections

When viewed from the underside of the base, the electrical connections are assigned as follows:

Note: Pins designated as Internal Connection (IC) must not be used for external circuit junctions or tie points. The tube must be operated strictly with the cathode negative and the anode positive.

To ensure mechanical reliability and prevent premature failure, the tube must not be subjected to severe shock or continuous vibration.

Electrical Characteristics and Ignition

Measured at an ambient temperature of between 20°C and 30°C, the initial electrical characteristics of the 150B2 are highly controlled:

• Maintaining Voltage ($V_a$): Nominally 150 V. At a continuous cathode current of 10 mA, the initial maintaining voltage is guaranteed to remain between a minimum of 146 V and a maximum of 151 V (with some specifications allowing up to 154 V).
• Ignition Voltage ($V_{ign}$): Under normal ambient illumination of 50 to 500 lux, the maximum voltage required to initiate discharge is 180 V. In complete darkness, the maximum required ignition voltage increases to 225 V.
• Supply Voltage ($V_b$): A minimum supply voltage of 180 V is required to guarantee reliable ignition throughout the entire operating life of the tube.
• Regulation Voltage: When the cathode current is varied from 5.0 to 15 mA, the increase in maintaining voltage is limited to a maximum of 5.0 V, with an average variation of 3.0 V.
• Temperature Coefficient: The temperature coefficient of the maintaining voltage at 10 mA is approximately 0.007% per °C (or 10 mV/°C).
• Incremental Resistance: At a cathode current of 10 mA, the incremental resistance is approximately 250 Ω. The incremental resistance becomes positive at cathode currents exceeding 5.0 mA.
• Voltage Jumps: Within the cathode current range of 10 to 15 mA, typical maximum voltage jumps are restricted to 75 mV.

Absolute Maximum Ratings

To prevent damage and ensure the rated operating life, the 150B2 must be operated within the following absolute maximum limits:

Operating Notes

1. Thermal Equilibrium: The tube reaches full thermal equilibrium within 3 minutes of ignition.
2. Surge Current Restriction: Operation at the maximum surge current of 40 mA must be restricted to a maximum duration of 30 seconds (or up to 40 seconds depending on the specification) in any 8-hour period of use to preserve tube life.

Long-Term Stability and Life Performance

When operated continuously at the specified currents, the 150B2 exhibits highly stable long-term performance at room temperature:

• Maintaining Voltage Variation:
  • In 1,000 hours at 10 mA: Maximum variation of +1% to -0.5% (or a maximum overall variation of 1%).
  • In 10,000 hours at 5 and 10 mA: Typical maximum variation of +2% to -1%.
  • In 30,000 hours at 5 and 10 mA: Typical maximum variation of +2% to -1%.
• Regulation Degradation: The typical maximum increase in maintaining voltage when the cathode current is swept from 5.0 to 15 mA degrades slightly over time:
  • In 1,000 hours: Maximum regulation voltage increase of 4.0 V.
  • In 10,000 hours: Maximum regulation voltage increase of 6.0 V.

Operating Curves and Ignition Dynamics

The ignition delay of the 150B2 in dark environments is characterized by a cumulative probability distribution. The time required for the tube to ignite is statistically dependent on the applied supply voltage; generally, an increase in the supply voltage significantly reduces the dark ignition delay time.

The relationship between the operating anode voltage ($V_a$) and the anode current ($I_a$) is bounded by defined upper and lower voltage limits. These limits outline the acceptable envelope of operation from 2 mA up to 14 mA, ensuring that the maintaining voltage remains stable and predictable within the specified current boundaries.