SLOS481B July 2010 – October 2014 LM833

PRODUCTION DATA.

- 1 Features
- 2 Applications
- 3 Description
- 4 Typical Design Example Audio Pre-Amplifier
- 5 Revision History
- 6 Pin Configuration and Functions
- 7 Specifications
- 8 Detailed Description
- 9 Application and Implementation
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information

- DGK|8

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

An application of the LM833 is the two stage RIAA Phono Preamplifier. A primary task of the phono preamplifier is to provide gain (usually 30 to 40 dB at 1 kHz) and accurate amplitude and phase equalization to the signal from a moving magnet or a moving coil cartridge. In addition to the amplification and equalization functions, the phono preamp must not add significant noise or distortion to the signal from the cartridge. The circuit shown in Figure 36 uses two amplifiers, fulfills these qualifications, and has greatly improved performance over a single-amplifier design.

- Supply Voltage = ±15 V
- Low-Frequency −3 dB corner of the first amplifier (f
_{0}) > 20 Hz (below audible range) - Low-Frequency −3 dB corner of the second stage (f
_{L}) = 20.2 Hz

Equation 1 through Equation 5 show the design equations for the preamplifier.

Equation 1. R_{1} = 8.058 R_{0}A_{1}

where

- A
_{1}is the 1 kHz voltage gain of the first amplifier

Equation 2.

Equation 3.

Equation 4.

Equation 5.

where

- f
_{L}is the low-frequency −3 dB corner of the second stage

For standard RIAA preamplifiers, f_{L} should be kept well below the audible frequency range. If the preamplifier is to follow the IEC recommendation (IEC Publication 98, Amendment #4), f_{L} should equal 20.2 Hz.

Equation 6.

where

- A
_{V2}is the voltage gain of the second amplifier

Equation 7.

where

- f
_{0}is the low-frequency −3 dB corner of the first amplifier

This should be kept well below the audible frequency range.

A design procedure is shown below with an illustrative example using 1% tolerance E96 components for close conformance to the ideal RIAA curve. Because 1% tolerance capacitors are often difficult to find except in 5% or 10% standard values, the design procedure calls for re-calculation of a few component values so that standard capacitor values can be used.

A design procedure is shown below with an illustrative example using 1% tolerance E96 components for close conformance to the ideal RIAA curve. Since 1% tolerance capacitors are often difficult to find except in 5% or 10% standard values, the design procedure calls for re-calculation of a few component values so that standard capacitor values can be used.

Choose R_{0}. R_{0} should be small for minimum noise contribution, but not so small that the feedback network excessively loads the amplifier.

Example: Choose R_{0} = 500

Choose 1 kHz gain, A_{V1} of first amplifier. This will typically be around 20 dB to 30 dB.

Example: Choose A_{V1} = 26 dB = 20

Calculate R_{1} = 8.058 R_{0}A_{V1}

Example: R_{1} = 8.058 × 500 × 20 = 80.58 k

Equation 8.

Equation 9.

If C_{1} is not a convenient value, choose the nearest convenient value and calculate a new R_{1} from Equation 10.

Equation 10.

Example: New C_{1} = 0.039 μF.

Equation 11.

Calculate a new value for R_{0} from Equation 12.

Equation 12.

Equation 13.

Use R_{0} = 499.

Equation 14.

Use R_{2} = 8.45 K.

Choose a convenient value for C_{3} in the range from 0.01 μF to 0.05 μF.

Example: C_{3} = 0.033 μF

Equation 15.

Choose a standard value for R_{3} that is slightly larger than R_{P}.

Example: R_{3} = 2.37 k

Calculate R_{6} from 1 / R_{6} = 1 / R_{P} − 1 / R_{3}

Example: R_{6} = 55.36 k

Use 54.9 k

Calculate C_{4} for low-frequency rolloff below 1 Hz from design Equation 5.

Example: C_{4} = 2 μF. Use a good quality mylar, polystyrene, or polypropylene.

Choose gain of second amplifier.

Example: The 1 kHz gain up to the input of the second amplifier is about 26 dB for this example. For an overall 1 kHz gain equal to about 36 dB we choose:

A_{V2} = 10 dB = 3.16

Choose value for R4.

Example: R_{4} = 2 k

Calculate R_{5} = (A_{V2} − 1) R_{4}

Example: R_{5} = 4.32 k

Use R_{5} = 4.3 k

Calculate C_{0} for low-frequency rolloff below 1 Hz from design Equation 7.

Example: C_{0} = 200 μF

The maximum observed error for the prototype was 0.1 dB.

The lower curve is for an output level of 300 mV_{rms} and the upper curve is for an output level of 1 V_{rms}.

While all the previously stated operating characteristics are specified with 100-pF load capacitance, the LM833 device can drive higher-capacitance loads. However, as the load capacitance increases, the resulting response pole occurs at lower frequencies, causing ringing, peaking, or oscillation. The value of the load capacitance at which oscillation occurs varies from lot-to-lot. If an application appears to be sensitive to oscillation due to load capacitance, adding a small resistance in series with the load should alleviate the problem (see Figure 39).