LearnTronics

NE5534

The NE5534 is a classic single low-noise bipolar-input operational amplifier intended for audio and other precision analog work. It offers low voltage noise, useful output drive and high speed, but it also has a design detail that deserves attention: its internal frequency compensation is intended for closed-loop gains of three or greater.

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At a glance

Item	NE5534 reference value / note
Amplifiers per package	1
Through-hole package used by LearnTronics	8-pin PDIP, commonly NE5534P
Equivalent input voltage noise	3.5 nV/√Hz typical
Unity-gain bandwidth	10 MHz typical
Slew rate	13 V/µs typical with no external compensation capacitor
CMRR	100 dB typical
Typical supply current	About 4 mA at the data-sheet test conditions
Current TI recommended supply rails	VCC+ = +5 to +15 V and VCC− = −5 to −15 V
Compensation	Internally compensated for closed-loop gain ≥ 3; external compensation is available

Reference: Texas Instruments NE5534/NE5534A/SA5534/SA5534A data sheet.

8-pin pinout

Pin	Name	Function
1	BALANCE	Offset / compensation function
2	IN−	Inverting input
3	IN+	Non-inverting input
4	VCC−	Negative supply, or ground in a single-supply circuit
5	COMP	External compensation / offset function
6	OUT	Amplifier output
7	VCC+	Positive supply
8	COMP/BAL	External compensation / offset function

Useful op-amp equations

Non-inverting amplifier

A_V = 1 + (R_F / R_G)

If RF = 20 kΩ and RG = 10 kΩ, the closed-loop voltage gain is 1 + 20k/10k = 3. That matters to an NE5534 because a gain of three is the region for which its internal compensation is intended.

Inverting amplifier

A_V = −R_F / R_IN

Single-supply midpoint bias

V_BIAS = V_S × R_bottom / (R_top + R_bottom)

In the FJD µ-Amp, two equal 100 kΩ resistors divide a nominal 9 V battery:

9 V × 100k / (100k + 100k) = 4.5 V

The op amp can then treat 4.5 V as the AC signal's working midpoint even though the circuit uses only a positive battery supply and ground.

Coupling-capacitor high-pass corner

f_c = 1 / (2πRC)

A coupling capacitor and the resistance it drives form a high-pass network. Increasing either R or C lowers the corner frequency and preserves more bass.

Why the 22 pF capacitor matters

The NE5534 is not simply a drop-in unity-gain-stable op amp under every condition. Texas Instruments states that it is internally compensated for a gain of three or greater and provides pins for external frequency compensation. The FJD µ-Amp uses a 22 pF compensation capacitor between the compensation pins.

A value written as 22 pF is 22 × 10⁻¹² farad. Confusing 22 pF with 0.1 µF would make the capacitor about 4.5 million times larger. Unit prefixes matter.

The FJD guitar µ-Amp and the 9 V question

The historical µ-Amp section operates the NE5534 from a single nominal 9 V battery and biases the signal near 4.5 V. That circuit arrangement is electrically understandable, but there is an important data-sheet lesson here.

The current TI data sheet lists recommended operating rails of +5 to +15 V and −5 to −15 V, equivalent to at least 10 V total supply. A 9 V battery is therefore slightly below the current recommended operating range. A circuit can function on the bench outside a published recommended range, but the manufacturer does not guarantee the published performance there.

This is a useful distinction for electronics work: absolute maximum, recommended operating, typical test conditions, and what happens to work in one prototype are not the same thing.

Used in LearnTronics

The NE5534 is used in the µ-Amp section of the FJD Six-String Piezo Guitar Electronics project. That circuit also uses 1 µF coupling capacitors, the 100 kΩ / 100 kΩ midpoint divider, and the 22 pF compensation capacitor.

Texas Instruments data sheet

LearnTronics treats manufacturer data sheets as the authority for limits and specifications. Verify the exact manufacturer, suffix, package and revision before substituting or building.