Simple Microphone (MIC) Amplifier Circuits

The first one is a single transistor simple microphone circuit, very simple to hook up using an electret microphone or MIC and an audio amplifier.

Typically the 10K resistor within the microphone's positive port offers this specific vital voltage for the procedure. The capacitor of 100nF on that particular network prevents the DC component of the transmission permitting the AC from the audio to get into the transistor amplifier through its base.

The 10K resistor attached to the transistor through its collector enables the triggering of that component, while the 100K causes the feedback of the signal. The output capacitor obstructs the DC component making just the audio signal to go to the following stage.

The circuit could be driven using any voltage between 3 and 9 volts not really being stabilized. However it is crucial that this supply is nicely filtered and decoupled. With regard to this, it is easy to put a 100μF capacitor together with a 100nF capacitor in parallel with the power line within the circuit.

This second design is a very handy little dynamic microphone amplifier circuit for amplifying weaker audio signal coming from a capacitive condenser microphone.

You may use this kind of dynami MIC amplifier circuit for audio sensing purposes and several programmed robotic receptors.

This particular condenser microphone DIY audio audio amplifier is extremely tiny and straightforward to utilize since it makes use of only a couple of general purpose transistors plus some discrete components.

You are able to build this circuit using a minimal price. This circuit is suitable for inexpensive sound amplification requirements in electronics for example pre-amplifier for FM audio receivers.
Circuit diagram

Audio amplifier circuit
Components required

Resistors 1K, and 100K 1/4 watt
Capacitors (10uF)
Transistors any small signal type such BC547 or 2N3053
Condenser mic
Speaker (8Ω, ½ Watt)

Working of amplifier

The two transistor MIC amplifier circuit is isolated into three sections: Condenser mic, audio amplifier and loudspeaker.

Condenser microphone is really a type of capacitive sound sensor (audio transducer) that will switch the sound (audio) signal directly into electrical impulses.

These electrical impulses tend to be far too weak it is therefore amplified through the amplifier unit. The increased output is acquired over the loudspeaker.

The output of condenser mic is actually combined by using a coupling capacitor of 10µF, the objective of this capacitor would be to eliminate DC material in the audio transmission.

A 1kΩ resistor is employed to offer the necessary biasing to the condenser microphone.

Transistor Q1 is set up as collector to base biasing function. This really is achieved through 100kΩ resistance. This resistor offers negative feedback for the transistor Q1.

The output of Q1 reaches at the collector (throughout 1kΩ resistor), that is the input to the transistor Q2 through a 0.1µF capacitor. The capacitor eliminates DC voltages because of the biasing of Q1.

Transistor Q2 is designed like fixed bias by using a 100kΩ resistor. Additionally, it offers additional amplification.

The amplified output through Q2 can be obtained over the 1kΩ resistor.
The 10µF electrolytic capacitor likewise employed to block the DC voltages of this particular biasing of transistor Q2.

Work with a 8Ω, ½ watt speaker to listen to the amplified signal.

5 Input Microphone Mixer Amplifier Circuit using a Single IC

This circuit enables the user to blend in one 5 separate signals from 5 dynamic low-impedance microphones and a couple of external auxiliary inputs, which can be electret-type microphones or even actually amplified inputs for example those from your CD player or a phone.

The circuit really is easy and is made up of feedback preamplifier stage, wherein input is positioned through a system of seven signals.

In the beginning I believed this circuit was intended to be for use in an outdoor system attached to a telephone mixture. Therefore several microphones and only a couple of auxiliaries were involved.

Within the auxiliaries hook up a micro electret which usually adequately catches the background noise and in other signals, through a resistance of 100K in series which doesn't show up in the diagram, hook up any convenient that enables to key in to the air Which can be faraway from where the system is positioned.

The overall performance of the circuit is extremely decent, because it simply needs 12V for its power could be provided from both a battery and a DC adapter source. The usage is incredibly low (around 10mA) and also the audio quality is extremely good.

Naturally, being anything specifically within the phone had been developed in mono settings, however nothing at all inhibits you from mounting a couple of equivalent circuits with double potentiometers and create it into a full fledged stereo mic mixture circuit.

Inside the microphone inputs you should make use of 6.5mm mono female plugs being that they are standard on lower Z microphones. The auxiliary inputs as an alternative tend to be freer. for me I used MiniDIN chips, such as the types used in the brand new PC's mouse.

These types of chips are extremely affordable and have a mechanised contact protection better than typical 3.5mm stereo.

Utilizing three terminals on the auxiliary inputs, the signal input and the polarization voltage (BIAS) needed regarding a micro electret could be delivered through various routes.

In case an amplified transmission is presented at the input, you should never hook up the polarized voltage please remember to put the resistance of 100K within the connector.

Microphone Amplifier Circuit with Bass Treble

The post details regarding a simple microphone (MIC) amplifier circuit which includes built in bass and treble control feature.

The active components of the circuit (amplifiers A1 and A2) proven in figure 1 are within IC1.

A1 runs as a non-inverting amplifier along with the microphone input is given to pin 1 through coupling capacitor C1.

The amplification aspect of this stage depends upon the ratio of resistor R5 to the parallel combined R1 . . . R4. Along with R1 turned in, the amplification point is approximately 225, together with R3 moved in around 60, along with S1 in the middle location around 14.

Since the efficient input level of sensitivity could be changed through S1, it may be aided to various input ranges or microphones.

The output of A1 is given to a tone control stage, A2. The proportion R13/R12 decides the amplification (around 18dB) in this stage.

The result of R11 and C6 is actually, in theory, much like that of R2 and C2: a smaller sized value of C6 raises the lower cut-off frequency. The RC system between A1 and A2 may be the actual tone control.

Potentiometer P1 fixes the bass level and P2 the treble level. Utilization is made from the attribute of capacitors performing as frequency centered resistances for ac voltages.

The output signal of the amplifier can be obtained to get link with the main amplifier through C9 and potentiometer P3.

This particular microphone amplifier circuit has not just already been tested in the Elektor laboratories but additionally from the designer in the course of browsing on-stage tests.

A printed circuit board with this low noise amplifier can be obtained. lt is extremely narrow to allow it to be applied as an input module within a mixer.

Low impedance microphone amplifier

Low impedence microphone are cheap and having more availability in the market. In case a high impedance microphone is used with any standard amplifier it is expected to give a better result though cost wise it is higher.

In order to accommodate a low input microphone in a microphone amplifier as shown in the circuit an additional staff with a high gain transistor T1 is needed.

In case a high impedance microphone is being used the signal can be directly connected to the junction point of capacitor C7 and the collector of the transistor.

In this circuit the operational amplifier used is TL081 which is a low noise amplifier thus producing higher audio quality compare to its brethren. For any audio amplifier circuit the power supply is of highest importance.

This circuit operates between 6 to 30V DC. It is to be ensured that the power supply is steady and with minimum ripple to achieve the desired result.

Parts List for the above Low impedance microphone amplifier circuit

all resistors are 1/4 watt 5% unless stated

• R1=15k
• R2= 150k
• R3= 2k2
• R4= 820
• R6= 10k
• R7= 10k
• P1= 1M
• C1= 3k9
• C2= 100u
• C3= 22u
• C4= 4u7
• C5= 470u
• C6= 10u
• C7= 100n
• C8= 47u nonpolar
• D1= 1N4148
• U1= TL081
• CN1= SIL6

Microphone Amplifier with Mute Switch

Microphones themselves can produce a very low output; a pre-amplifier must be used to bring up the signal to an appropriate level. The signal-to-noise ratio plays a major role in this due to the input being a small signal.

We will be discussing both a symmetrical and an asymmetrical circuit for a pre-amplifier that can be used for almost all purposes. A useful addition here is the mute switch that both speakers and audience members will be thankful for in case the speaker needs to cough, sneeze or clear their throat. You will see any low-noise operational amplifiers these days. So these pre-amplifiers will be comparatively low-cost.

The first figure above is of the asymmetrical version. Switch S2 enables you to flip between high and low impedance matching. The set-up here of opamp A1 is that of an AC amplifier with an approximate 27dB gain. If R3 and C1 are removed and R2 brought down to 22 k, this can be used as a DC amplifier. The function of capacitor C2 is to cap the bandwidth of the amplifier for stable working.

C3 is used to block the DC component in the amplifier output, whether used as a DC amplifier or an AC one.

The AC signal, upon amplification, goes to the muting stage T1, a field-effect transistor or FET. In normal circumstances, it conducts and leads the output to A2 where it is further amplified by 5. The signal is then passed through high-pass filter R13-C6 to the output terminal. The load should be over 10 kΩ.

On pressing the mute switch S1, a negative voltage is passed to the FET at its gate, which switches it off. The speed of muting is decided by capacitor C5 within specific limits. You can use electrolytic capacitors for C1, C3 and C6. The right direction to connect them is found by measuring the DC level at the two terminals for each.

Figure 2 shows the circuit for the symmetrical input. It is different from the asymmetric version in that it has A1, A2 and A3 connected at the input stage for symmetry. The A1 and A2 opamps give a cumulative gain of 20 dB, while opamp A3 acts as a differential amplifier to hinder the common-mode noise and interference.