Data set 01
1961 Tung Sol
Published operating points and test conditions from this source.
SECTION 1
Triode
Other
Plate Voltage
150 V
Characteristic
Plate Current
6 mA
Voltage - Dual Triode (similar) ·Triode-Triode
12AZ7A
High-mu miniature twin triode for resistance-coupled voltage amplification and phase inversion, an improved 12AZ7-family version intended for general amplifier service.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 2
- Base
- 9A
- Socket code
- B9A
- Base pins
- 9
- Nominal heater
- 12.6 V / 225 mA
Description
12AZ7A — High-Mu Twin Triode
The 12AZ7A is a miniature, nine-pin double triode vacuum tube featuring two independent triode sections with a common heater. It is designed for a variety of high-frequency and audio applications, most notably as a grounded-grid radio frequency (RF) amplifier, a direct-coupled cathode-drive RF amplifier, or a combined oscillator-mixer in VHF television tuners (supporting both color and black-and-white systems). Additionally, the tube is suitable for audio amplifier applications.
While some technical descriptions classify the 12AZ7A as containing two independent medium-mu triodes, its typical amplification factor of 60 leads other references to designate it as a high-mu twin triode. Each triode section is electrically independent except for their shared heater connections.
Mechanical Construction, Base, and Pinout
The 12AZ7A is constructed in a miniature T-6 1/2 glass bulb with a small-button noval 9-pin base (JEDEC No. E9-1, outline drawing JEDEC 6-2). The tube features coated unipotential cathodes and can be operated in any mounting position.
Physical Dimensions
- Maximum Overall Length: 2-3/16 inches (2.187 in)
- Maximum Seated Length: 1-15/16 inches (1.937 in)
- Length from Base Seat to Bulb Top (excluding tip): 1-9/16" ± 3/32"
- Diameter Range: 0.750 to 0.875 inches
Pin Connection Diagram (JEDEC 9A)
The 9A basing arrangement provides independent connections for both triode sections, viewed from the bottom of the tube:
| Pin | Connection |
|---|---|
| Pin 1 | Plate of Unit No. 2 |
| Pin 2 | Grid of Unit No. 2 |
| Pin 3 | Cathode of Unit No. 2 |
| Pin 4 | Heater of Unit No. 2 |
| Pin 5 | Heater of Unit No. 1 |
| Pin 6 | Plate of Unit No. 1 |
| Pin 7 | Grid of Unit No. 1 |
| Pin 8 | Cathode of Unit No. 1 |
| Pin 9 | Heater Tap |
Pins 4, 5, and 9 allow the heater to be wired in either a series or parallel configuration.
Heater Characteristics and Controlled Warm-Up
The 12AZ7A is designed with a controlled heater warm-up time, making it suitable for series-string or parallel heater circuits.
Heater Ratings and Supply Limits
- Series Connection:
- Nominal Voltage: 12.6 V (AC or DC)
- Voltage Supply Limits: 12.6 ± 1.3 V (or ±10%)
- Nominal Current: 0.225 A (225 mA)
- Parallel Connection:
- Nominal Voltage: 6.3 V (AC or DC)
- Current Supply Limits: 0.45 ± 6% A (450 ± 30 mA)
- Average Heater Warm-up Time: 11 seconds
The heater warm-up time is defined as the time required for the voltage across the heater to reach 80% of its rated voltage after applying 4 times the rated heater voltage to a circuit consisting of the tube heater in series with a resistance of value 3 times the nominal heater operating resistance.
Heater-Cathode Voltage Limits
The maximum allowable voltage between the heater and cathode depends on the rating system applied:
- Design-Maximum Ratings:
- Heater negative with respect to cathode: 200 V max (Total DC and Peak)
- Heater positive with respect to cathode: 200 V max (Total DC and Peak), with the DC component not exceeding 100 V.
- Design-Center Ratings:
- Maximum Heater-Cathode Voltage: 90 V
Electrical Characteristics and Typical Operating Points
The 12AZ7A exhibits high transconductance and moderate-to-high amplification. For typical Class A1 amplifier operation, the characteristics of each individual triode section are evaluated at two primary operating points:
| Parameter | Operating Point A | Operating Point B |
|---|---|---|
| Plate Supply Voltage | 100 V | 250 V |
| Cathode Bias Resistor | 270 Ω | 200 Ω |
| Plate Current | 3.7 mA | 10 mA |
| Transconductance | 4,000 µmhos | 5,500 µmhos |
| Amplification Factor | 60 | 60 |
| Plate Resistance (Approx.) | 15,000 Ω | 10,900 Ω |
| Grid Voltage (Approx.) for | -5 V | -12 V |
For additional Class A1 amplifier characteristics and curves, technical references specify that the curves and characteristics shown under miniature type 12AT7 also apply directly to the 12AZ7A.
Interelectrode Capacitances
The direct interelectrode capacitances of the 12AZ7A vary depending on whether an external shield is used. Measurements with a shield are typically performed using JEDEC No. 315 external shield connected to the cathode of the unit under test.
Standard Operation (Each Section)
Two sets of values are documented in technical specifications, reflecting minor variations in measurement conditions:
| Capacitance Parameter | Unshielded (Set 1) | Shielded (Set 1) | Unshielded (Set 2) | Shielded (Set 2) |
|---|---|---|---|---|
| Grid to Plate | 2.0 pF | 1.9 pF | 1.9 pF | 1.9 pF |
| Input (Grid to Cathode + Heater) | 2.6 pF | 2.8 pF | 3.1 pF | 3.2 pF |
| Output (Plate to Cathode + Heater) - Unit 1 | 0.44 pF | 1.4 pF | 0.5 pF | 1.3 pF |
| Output (Plate to Cathode + Heater) - Unit 2 | 0.36 pF | 1.6 pF | 0.4 pF | 1.6 pF |
Grounded-Grid Operation (Each Section)
For high-frequency grounded-grid applications, the capacitances are specified as follows:
| Capacitance Parameter | Unshielded | Shielded |
|---|---|---|
| Input (Each Section) | 6.9 pF | 7.0 pF |
| Output (Section 1) | 2.0 pF | 2.8 pF |
| Output (Section 2) | 2.0 pF | 3.2 pF |
| Plate to Cathode | 0.24 pF | 0.23 pF |
Maximum Ratings and Circuit Constraints
To ensure reliable operation and prevent premature failure, circuit designers must adhere to the maximum ratings. These ratings are published under two different rating systems and must not be exceeded.
Maximum Ratings Comparison
| Parameter | Design-Maximum Values | Design-Center Values |
|---|---|---|
| Plate Voltage | 330 V | 300 V |
| Negative Grid Voltage | 55 V | 50 V |
| Plate Dissipation (Each Section) | 2.5 W | 2.5 W |
| Total Plate Dissipation (Both Sections) | 5.0 W | — |
Maximum Grid-Circuit Resistance
The maximum allowable resistance in the grid circuit of each unit is constrained by the biasing method to prevent thermal runaway:
- For Fixed-Bias Operation: 0.25 Megohm maximum
- For Cathode-Bias (Self-Bias) Operation: 1.0 Megohm maximum
Socket description
Small-button Noval 9-contact
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- 9A
- Socket code
- B9A
- Base pins
- 9
- Nominal heater voltage
- 12.6 V
- Nominal heater current
- 225 mA
- Parallel heater voltage
- 6.3 V
- Parallel heater current
- 450 mA
- Series capable
- Yes
9A - Terminal pinout
Electrical assignments shared by every tube using this base designation.
| Terminal | Section | Connection | Evidence |
|---|---|---|---|
| PIN12P | B | P — Plate (Anode) EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN22G1 | B | G1 — Control Grid EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN32K | B | K — Cathode EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN4H | — | H — Heater EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN5H | — | H — Heater EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN61P | A | P — Plate (Anode) EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN71G1 | A | G1 — Control Grid EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN81K | A | K — Cathode EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
| PIN9HCT | — | HCT — Heater Center Tap EIA transcription; manufacturer confirmation pending | Unverified EIA Base Connections, printed page 130, 9A |
Section ratings
2 physical sections, each with unique specifications.
Section 1
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 10900 Ω
- Transconductance
- 0.0055 S
- Amplification factor
- 60
- Max plate voltage
- 330 V
- Max plate dissipation
- 2.5 W
Representative row for electrically identical repeated sections.
Section 2
Triode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 10900 Ω
- Transconductance
- 0.0055 S
- Amplification factor
- 60
- Max plate voltage
- 330 V
- Max plate dissipation
- 2.5 W
High-mu controlled-warm-up triode; curves shared with 12AT7.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 02
1966 Tung Sol Electronic Tubes 2 of 4
Published operating points and test conditions from this source.
SECTION 1
Triode
Capacitance
GRID TO PLATE: (G TO P) EACH SECTION
1.9 pF
Published datasheet; operating column 1
GRID TO PLATE: (G TO P) EACH SECTION
2 pF
Published datasheet; operating column 2
Other
INPUT; G TO (H+K) EACH SECTION
2.8 pF
Published datasheet; operating column 1
INPUT; G TO (H+K) EACH SECTION
2.6 pF
Published datasheet; operating column 2
HEATER IN SERIES
12.6 mA
Published datasheet; operating column 1
HEATER IN SERIES
225 mA
Published datasheet; operating column 2
HEATER IN PARALLEL
6.3 mA
Published datasheet; operating column 1
HEATER IN PARALLEL
450 mA
Published datasheet; operating column 2
HEATER WARM-UP TIME
8 s
Published datasheet; operating column 1
HEATER WARM-UP TIME
11 s
Published datasheet; operating column 2
TOTAL DC AND PEAK
200 V
Published datasheet
PLATE DISSIPATION (EACH SECTION)
2.5 W
Published datasheet
TOTAL PLATE DISSIPATION
5 W
Published datasheet
FIXED BIAS
0.25 Mohm
Published datasheet
SELF BIAS
1 Mohm
Published datasheet
CATHODE BIAS RESISTOR
270 ohm
Published datasheet; operating column 1
CATHODE BIAS RESISTOR
200 ohm
Published datasheet; operating column 2
CATHODE BIAS RESISTOR
0 ohm
Published datasheet; operating column 3
Maximum plate voltage
300 V
Published datasheet; promoted section value
Maximum plate dissipation
2.5 W
Published datasheet; promoted section value
Characteristic
VOLTAGE
0 V
Published datasheet; operating column 1
VOLTAGE
12.6 V
Published datasheet; operating column 2
VOLTAGE
1.3 V
Published datasheet; operating column 3
CURRENT
0 mA
Published datasheet; operating column 1
CURRENT
450 mA
Published datasheet; operating column 2
CURRENT
30 mA
Published datasheet; operating column 3
PLATE VOLTAGE
330 V
Published datasheet
NEGATIVE DC GRID VOLTAGE
55 V
Published datasheet
PLATE VOLTAGE
100 V
Published datasheet; operating column 1
PLATE VOLTAGE
250 V
Published datasheet; operating column 2
PLATE CURRENT
3.7 mA
Published datasheet; operating column 1
PLATE CURRENT
10 mA
Published datasheet; operating column 2
PLATE RESISTANCE (APPROX.)
15000 ohm
Published datasheet; operating column 1
PLATE RESISTANCE (APPROX.)
10900 ohm
Published datasheet; operating column 2
PLATE RESISTANCE (APPROX.)
0 ohm
Published datasheet; operating column 3
FOR
16 V
Published datasheet; operating column 1
FOR
101 V
Published datasheet; operating column 2
FOR
-5 V
Published datasheet; operating column 3
Plate resistance
10900 ohm
Published datasheet; promoted section value
Transconductance
0.0055 A/V
Published datasheet; promoted section value
Amplification factor
60
Published datasheet; promoted section value
Data set 03
1971 RCA HB3 Binder 5 of 7
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristics
Heater voltage series
12.6 V
SeriesHeater
Heater current series
225 mA
SeriesHeater
Heater voltage parallel
6.3 V
ParallelHeater
Heater current parallel
450 mA
ParallelHeater
Heater warm-up time
11 s
Average
Plate supply voltage
100 V
ClassA1;PublishedPoint1
Plate supply voltage
250 V
ClassA1;PublishedPoint2
Cathode resistor
270 ohm
ClassA1;PublishedPoint1
Cathode resistor
200 ohm
ClassA1;PublishedPoint2
Amplification factor
60
ClassA1
Plate resistance
15000 ohm
ClassA1;PublishedPoint1
Plate resistance
10900 ohm
ClassA1;PublishedPoint2
Transconductance
4000 µS
ClassA1;PublishedPoint1
Transconductance
5500 µS
ClassA1;PublishedPoint2
Plate current
3.7 mA
ClassA1;PublishedPoint1
Plate current
10 mA
ClassA1;PublishedPoint2
Other
Maximum plate voltage
330 V
ClassA1
Maximum negative grid bias
55 V
ClassA1
Maximum plate dissipation
2.5 W
ClassA1
Peak heater-cathode voltage
200 V
Capacitance
Grid-to-plate capacitance
2 pF
WithoutExternalShield
Grid-to-plate capacitance
1.9 pF
WithExternalShield
Grid-to-cathode-and-heater capacitance
2.6 pF
WithoutExternalShield
Grid-to-cathode-and-heater capacitance
2.8 pF
WithExternalShield
Plate-to-cathode-and-heater capacitance
0.44 pF
WithoutExternalShield
Plate-to-cathode-and-heater capacitance
1.4 pF
WithExternalShield
SECTION 2
Triode
Characteristics
Heater voltage series
12.6 V
SeriesHeater
Heater current series
225 mA
SeriesHeater
Heater voltage parallel
6.3 V
ParallelHeater
Heater current parallel
450 mA
ParallelHeater
Heater warm-up time
11 s
Average
Plate supply voltage
100 V
ClassA1;PublishedPoint1
Plate supply voltage
250 V
ClassA1;PublishedPoint2
Cathode resistor
270 ohm
ClassA1;PublishedPoint1
Cathode resistor
200 ohm
ClassA1;PublishedPoint2
Amplification factor
60
ClassA1
Plate resistance
15000 ohm
ClassA1;PublishedPoint1
Plate resistance
10900 ohm
ClassA1;PublishedPoint2
Transconductance
4000 µS
ClassA1;PublishedPoint1
Transconductance
5500 µS
ClassA1;PublishedPoint2
Plate current
3.7 mA
ClassA1;PublishedPoint1
Plate current
10 mA
ClassA1;PublishedPoint2
Other
Maximum plate voltage
330 V
ClassA1
Maximum negative grid bias
55 V
ClassA1
Maximum plate dissipation
2.5 W
ClassA1
Peak heater-cathode voltage
200 V
Capacitance
Grid-to-plate capacitance
2 pF
WithoutExternalShield
Grid-to-plate capacitance
1.9 pF
WithExternalShield
Grid-to-cathode-and-heater capacitance
2.6 pF
WithoutExternalShield
Grid-to-cathode-and-heater capacitance
2.8 pF
WithExternalShield
Plate-to-cathode-and-heater capacitance
0.36 pF
WithoutExternalShield
Plate-to-cathode-and-heater capacitance
1.6 pF
WithExternalShield
Data set 04
1975 RCA RC30
Published operating points and test conditions from this source.
SECTION 1
Triode
Characteristic
Plate Resistance
22800 ohms
Published value from supplied target entry
Transconductance
1750
Published value from supplied target entry
Plate Current
3 mA
Published value from supplied target entry
Grid Voltage (Approx.) for plate current of
11 mA
Published value from supplied target entry
Heater Warm-up Time (Average)
11 seconds
Published value from supplied target entry
Plate Voltage
330 volts
Published value from supplied target entry
Grid Voltage, Negative-bias value
55 volts
Published value from supplied target entry
Plate Dissipation
2.5 watts
Published value from supplied target entry
Heater Voltage
6.3 volts
Published value from supplied target entry
Heater Current
0.6 ampere
Published value from supplied target entry
Heater Warm-up Time
11 seconds
Published value from supplied target entry
Plate Voltage
550 volts
Published value from supplied target entry
Grid Voltage, Negative-bias value
50 volts
Published value from supplied target entry
Plate Dissipation
5.5 watts
Published value from supplied target entry
Plate Voltage
150 volts
Published value from supplied target entry
Grid Voltage
-17.5 volts
Published value from supplied target entry
Amplification Factor
6.5
Published value from supplied target entry
Plate Resistance (Approx.)
1030 ohms
Published value from supplied target entry
Transconductance
6300
Published value from supplied target entry
Plate Current
34
Published value from supplied target entry
Grid Voltage (Approx.) for plate current of
-32 volts
Published value from supplied target entry
DC Plate Voltage
550 volts
Published value from supplied target entry
Capacitance
Grid to Plate (Each unit)
1.9 pF
Published value from supplied target entry
Grid to Cathode and Heater (Each unit)
2.8 pF
Published value from supplied target entry
Grid to Plate
4.8 pF
Published value from supplied target entry
Grid to Cathode and Heater
5 pF
Published value from supplied target entry
Plate to Cathode and Heater
-5 pF
Published value from supplied target entry